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Transcript of Midwest Mapping Project IL
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By Michael P. McDonald
Midwest Mapping Project
IllInoIs
MIchIgan
MInnesota
ohIo
WIsconsIn
house
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Executive Summary
Redistricting is the drawing o legislative district boundaries. It usually occurs ollowing the decen-nial census so that districts will have approximately equal population and thus their constituents
will have approximately equal representation. However, there is much more to it. How districts are
drawn afects the ortunes o political parties, careers o incumbents, and representation o minori-
ties. Oen those who draw the districts are the same people who represent the districts, enabling an
abuse known as gerrymandering. During redistricting it is thus the case that representatives may
select voters rather than voters elect representatives.
A proposed solution to gerrymandering, and as a byproduct produce pleasing-looking districts, is
to have those who draw districts strictly ollow a set o neutral criteria. A computer might even be
programmed to automatically perorm this task. While this may sound like an attractive solution,
the Devil is in the details. Because people are not randomly scattered across the countryside, ap-
plication o ostensibly neutral criteria can intentionally or unintentionally have political efects. For
example, districts that respect city boundaries may overly concentrate supporters o a political party
i their supporters are clustered into dense urban areas. Instead o taking politics out o redistricting,
these neutral criteria may actually be a gerrymander in sheeps clothing.
Te purpose o this report is to investigate the potential efects o our criteria on the congressional
and state legislative districts that may be produced in the ve Midwestern states o Illinois, Michi-
gan, Minnesota, Ohio, and Wisconsin. o do so, congressional and state legislative plans are drawn
in accordance to our criteria, which are oen proposed as neutral criteria by reormers. Tere
are, o course, many other criteria that are oen proposed. Districts are drawn to look like squares
arrayed on a regular grid. Districts are drawn to be as compact as possible. Districts are drawn to re-
spect county boundaries. And districts are drawn to respect census place boundaries, which are cit-
ies, towns, and other governmental units that states and the Census Bureau work together to dene.
Tis mapping exercise demonstrates that it is practically di cult to achieve what may seem ideally
easy, such as drawing all districts to look like squares. Many practical details conound achieving
this ideal, perhaps the most important being that cities are densely populated. When districts must
be o equal population, as one moves rom densely populated urban areas to sparsely populated
rural areas, geographically smaller districts must give way to progressively larger districts. As a
consequence it is oen impossible to t districts together into nice shapes.
Tese our ways o drawing districts have predictable representational efects, both partisan and
racial. Tese efects are not always consistent or the our types o districts that are drawn across the
ve states or or the three types o legislative districts therein. Redistricting criteria should thus bethoughtully considered beore being adopted in any state. Tis is true even or diferent legislative
districts within the same state, since diferently sized districts such as large congressional districts
and small lower legislative chamber districts may interact with criteria in diferent ways.
An important lesson rom this report is that a one-size-ts-all approach to redistricting reorm will
not work in practice. Readers are encouraged to pay attention to all mapping scenarios within all
ve o these states. Doing so will illuminate the possibilities and limitations o redistricting reorm.
Tis mapping
exercise demon-
strates that it is
practically dif cult
to achieve what may
seem ideally easy.
Tese our ways o
drawing districts
have predictablerepresentational
eects, both partisan
and racial.
1 Introduction
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Acknowledgments
Tis report and the mapping project described herein were directed by Dr. Michael P. McDonald,
Associate Proessor o Government and Politics at George Mason University. Tis report made is
possible through painstaking mapping conducted by our George Mason University research assist-
ants: Nichole Claggett, Shaun Daniels, Gabriel Hudson, and Michael Keating. Helpul comments
on sections o this report were provided by Ann Henkener, Mike McCabe, Rich Robinson, and Rob
Richie. I am most grateul to odd Breitbart and Justin Levitt or their detailed comments o the
entire report. All errors remain my own. Tis project was generously unded by the Joyce Foundation
and benefted tremendously rom L arry Hansens participation. I would like to thank Caliper
Corporation or providing their mapping soware at a discount or this academic research. Finally,
I would like to thank the design team at Jasculca/erman and Associates or their expertise in pre-
paring this report.
Summary o Findings
Tis report examines redistricting within the fve Midwestern states o Illinois, Michigan, Minneso
ta, Ohio, and Wisconsin. For each state, congressional, upper legislative chamber, and lower legisla-
tive chamber districts are drawn under our criteria. Districts are drawn to look like squares arrayed
on a regular grid. Districts are drawn to be as compact as possible. Districts are drawn to respect
county boundaries. And districts are drawn to respect city boundaries. Te resulting collections o
districts known as redistricting plans are evaluated on their districts compactness, the number o
times districts split counties, their political composition, and their racial composition. Te mappin
oen reveals distinctive eatures o a state that aect redistricting, such as where people o dierent
races or political persuasion live or how natural eatures and political boundaries are laid out across
the state.
A summary o the lessons learned rom the mapping within each state is located at the beginning o
each states section. Some overarching themes emerge rom the state specifc fndings.
Where people live matters to redistricting. In particular, a proposed criterion may have predict-
able partisan or racial eects. Tis should seem-sel evident, but it is a simple act that that is oen
overlooked in redistricting reorm proposals.
Statewide plots showing where Democrats and Republicans live support the conventional wisdomthat Democrats tend to be concentrated within densely populated urban areas and Republicans ten
to be located within more sparsely populated suburban and rural areas. Te catch is that Democrati
communities tend to be places where ew Republicans live while Republican communities are inter
mixed with some Democrats.
Republican residential patterns tend to b e more e cient than Democrats rom a partisan gerry-
mandering standpoint.1 A gerrymandering strategy is to overly-concentrate an opponents sup-
porters into districts that they win easily. Tis technique to waste votes, known as packing, applies
Introduction 2 3 Introductio
Republican residen-
tial patterns tend
to be more ef cient
than Democrats
rom a partisan ger-
rymandering stand-
point.
able o Contents
Introduction
Summary o Findings p. 3
How to Draw Districts p. 5
Te Redistricting Data p. 6
Te Mapping Process p. 10
Map Statistics p. 12
Compactness Measures p. 14
Illinois
Overview p. 18
Congressional p. 22
State Legislature, Upper Chamber p. 32
State Legislature, Lower Chamber p. 42
Michigan
Overview p. 52
Congressional p. 56
State Legislature, Upper Chamber p. 66
State Legislature, Lower Chamber p. 76
Minnesota
Overview p. 86
Congressional p. 90
State Legislature, Upper Chamber p. 100
State Legislature, Lower Chamber p. 110
Ohio
Overview p. 120
Congressional p. 124
State Legislature, Upper Chamber p. 134
State Legislature, Lower Chamber p. 144
Wisconsin
Overview p. 154
Congressional p. 158
State Legislature, Upper Chamber p. 168
State Legislature, Lower Chamber p. 178
Endnotes p. 188
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to ederal Voting Rights requirements. Elsewhere, even though race is not s pecifcally considered
during map drawing, at least s ome minority-majority districts are drawn as a happenstance o
ollowing the our criteria. In Cleveland and Detroit, particularly, minority communities tend to
align along county and city lines. Some minority-majority districts are created when districts are
drawn that respect these political boundaries. Still, exploratory mapping to increase the number o
minority-majority districts indicates that there are some opportunities to do so beyond the number
realized in the 2000s plans i these political boundaries are crossed. In most instances, drawing test
plans ollowing the criteria used in this mapping project did not yield the same number o minority
majority districts as the adopted plan, which suggests that race may need to be taken into account t
satisy ederal Voting Rights requirements.
Te mapping reveals that there are practical limits to idealized districts that look like squares or
circles. For example, it is exceedingly di cult essentially impossible anywhere except perhaps or
Wyomings single congressional district to draw every district in a state to look like a square or
other compact shape. Densely-populated urban areas transition to sparsely-populated suburban an
rural areas. When equal population districts are overlaid on this population, districts must become
progressively larger in geographic size as population becomes more dispersed. As a result, there are
inevitably leover pieces in the transition zone that do not ft nicely into a district.
Tere are many ways proposed to measure a districts compactness. Te mapping reveals that these
compactness measures are related to specifc redistricting goals. Compactness measures that avor
minimal lengths o district perimeters tend to do well or square-shaped districts since census
blocks the building blocks o districts tend to ollow straight lines. Because census blocks do
not ollow circles, circular districts tend to are poorly on compactness measures avoring shorter
perimeter lengths and better on those that compare a district to an idealized circle. Districts drawn
around cities tend to are better on compactness measures that take into account where people live
within the district.
Te sum o our fndings is that one size does not ft all. Tis is true across states and across dierent
sized legislative districts within the same state. Toughtul consideration should be given to how
proposed redistricting criteria or legislative districts will interact with where a states residents live
Following neutral criteria, such as drawing districts to be squares or along some other seemingly
neutral criteria, may have predictable political consequences. I representational goals are a com-
ponent o a redistricting reorm proposal, these goals should be explicitly stated, rather than hoping
that a set o criteria will by ortunate happenstance produce a desired political outcome.
How to Draw Districts
o properly understand redistricting it is important to understand how to draw districts. Seemingly
technical details constrain redistricting in meaningul ways. For example, it is oen assumed even
by proessors that all groupings o individuals into districts are possible. However, this is not the
case. Practical geographic considerations actor in by the way the Census Bureau releases populatio
data to protect individuals confdentiality and by even the most modest requirement that districts
be compact.
5 Introductio
Toughtful consid-
eration should be
given to how pro-
posed redistricting
criteria for legisla-
tive districts will
interact with where
a states residents
live.
to any identifable group, including minorities. Because many Democrats tend to live in heavily
Democratic areas, districts that ollow neutral criteria will pack Democrats. Republicans are thus
generally observed to do better t han what their statewide strength would otherwise indicate among
the various test plans. Tere are comparatively more sae Democratic districts, while there are more
Republican-leaning competitive districts.
Unlocking Democrats rom urban centers can be achieved by drawing districts that tie together
Democratic urban areas and Republican suburban and rural areas. Depending on the degree by
which county or city boundaries overlay where people o dierent partisan stripes live, respecting
county or city borders can thus have predictable political consequences.
Democrats can be urther disadvantaged when large cities are located near a state border. In these
places the possibilities or unpacking Democrats are limited since a direction to draw districts is
unavailable. Tis dynamic occurs in Chicago, Illinois; Cincinnati, Ohio; Cleveland, Ohio; Detroit,
Michigan; and Milwaukee, Wisconsin.
Although geographic rules oen skew partisan representation in some instances, certain rules can have
a benefcial eect on partisan representativeness. Academics who study electoral systems around the
world note that single-member district systems tend to award the majority party with an additional
seat bonus above their share o votes. In an overwhelming Democratic state, a Democratic advantage
may be oset by the identifed redis tricting ine ciencies o where Democrats live, the reby making the
number o seats a party wins more reective o their statewide vote share. Te degree to which this is
true may depend on how districts are drawn in the remainder o a state. In Illinois and Michigan, the
ine ciencies o Democ rats concentrated in Chicago and Detroit may be parti ally oset by ollowing
criteria that result in consolidating mid-sized cities into Democratic-leaning districts. Tis is also true
in Wisconsin, though the rural areas o the state tend to be more balanced between Democrats and
Republicans than in other states examined in this report, urther mitigating the Republican advantage
realized during redistricting as a consequence o where people live.
Minnesota presents an interesting case o how the s ize o districts, relative to the size o cities, aects
the unpacking o Democrats. Te ideal equal-population or each o the states eight congressional
districts is 614,935 persons. Te ideal population or each o t he states one hundred and thirty-our
state House districts is 36,713 persons. In this relatively balanced battleground state, the partisan
composition o the congressional districts can reect the state as a whole i win Cities Democrats
are unpacked. Tis can be accomplished by drawing relatively compact districts that split the win
Cities core into our districts, grouping urban Democrats with suburban Republicans. ests plans o
State House districts exhibit more o a Republican advantage because these smaller districts cannot
bridge these urban and suburban areas. Tis disadvantage or Democrats is oset when plans are
specifcally drawn to respect census places, which creates additional Democratic districts Outstate
rom the win Cities. Interestingly, this Republican advantage is not mitigated among the statesslightly larger sixty-seven state Senate districts. Tese Senate districts tend to be larger than the
states mid-sized cities, as such these Senate districts must have a relatively greater mix o rural than
urban population compared to House districts.
Te ways by which the our ways o drawing districts aect racial representation is also examined.
Where minorities constitute a large enough population to constitute a majority o a district, minori-
ties tend to live in compact communities in urban centers. Illinois minority communities tend to be
the least compact o the fve states examined and thus require more consideration in order to adhere
INRODUCION
Introduction 4
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o illustrate, consider a map o the southern environs o Springfeld, Illinois. Census blocks appear
to mostly ollow roads and it is thus easy to identiy housing subdivisions on t his map. Note that no
all roads orm the border o a census block and not all census block borders are roads. City borders
water, and railroads also orm census block borders. In the top middle o the map, a census block
boundary cuts across an open feld, ollowing an old rail be d.
Some people suggest that states should be divided into square districts, but this map should disabus
anyone o the notion that square districts are easy to draw. Roads, terrain, and political boundaries
simply are not arrayed onto a ready-made grid.
Certainly, some o the limitations census geography places on redistricting are inconsequential, suc
as the intersection o I-55 and I-72 that orms the diamond-shape in the upper right-hand quadran
o the map. No one lives between the overpass and the connecting ramps, yet the Census Bureau ha
seen ft to designate these areas as s eparate census blocks. One might split or assign census blocks
such as these to more than one district without aecting districts populations. However, to split
census blocks where people live requires urther justifcation. Districts must be o equal population
so how the split divides a blocks population would need to be determined through sources other
than census data.
A urther complication that rustrates map drawing is that cities oen do not have regular boundar-
ies. An arm o Lake Springfeld, located along the bottom o the map, is within the city o Springfeld.
Some homes along the lake are incorporated within the city, while others remain within the county.
Tese annexation decisions have created oddly-shaped city borders throughout the map. Tere are
several examples o cities completely encompassed by larger cities, such as the city o Bexley located
within Columbus, Ohio and Hamtramck and Highland Park located within Detroit, Michigan.
A close examination o the map, particularly along the lake but also elsewhere, reveals that some
homes are actually located on islands o county land isolated within the city. In redistricting
terminology, these islands are non-contiguous to t he county proper. I one were to draw a district
composed solely o Springfeld, these islands would pose a quandary since contiguity is considered
a relatively non-controversial criterion that is sometimes even required by law.
Population Data: Redistricting occurs at least once a decade because in the 1960s the United State
Supreme Court interpreted the ederal constitution to require that districts be o substantially equa
population.3 At the time, s ome states had not redistricted or decades, creating severe population
imbalances between ast growing urban areas and slower growth rural areas. People living in under
populated rural districts were thereby aorded more representation than people living in overpopu
lated urban districts. Te equal population requirement means that redistricting now occurs at t he
start o each decade when population shis are revealed by a new decennial census.
Te 2000 census population data reported in t he Census Bureaus PL94-171 redistricting data fle,
which is so-called aer t he ederal law which mandates its release or redistricting purposes, are
used or mapping. Te PL94-171 fle is among the frst data that the Census Bureau releases ollow-
ing the decennial census. Processing decennial census data is a laborious task, and only a limited
amount o inormation is released in the PL94-171 fle. Te fle reports or all census blocks the tota
number o persons, those o voting age, and these statistics by race. Te race inormation enables
the drawing o districts that provide minority communities opportunities to elect candidates o the
choice, as required by the ederal Voting Rights Act.
7 Introductio
When districts are drawn, people do not s imply take a crayon to a piece o paper. Enormous
amounts o geospatial, population and election data are processed by computers and analyzed by
map drawers to ensure that the resulting districts conorm to ederal and state criteria and that the
redistricting plans will be politically acceptable to those who must vote to adopt them.
HE REDISRICING DAA
Redistricting data sets have three important components. Tere are geospatial data, which in the
world o modern technology are a digital representation o maps produced by the Census Bureau.
Tere are population data which the Census Bureau associates with their digital maps. And there are
election data that a redistricting authority may associate with the digital maps.
Geospatial Data: Trough the marvels o modern technology, the Census Bureau has digitally
mapped the entire country. Tis technological advancement is actually widely used, though most
people do not think much about it. It enables someone to look up a street address and plot direc-
tions rom their house to a destination o their choice.
Te Census Bureau does not publicly release their data in such a way that permits an individual
to look up an address to see how the people living there flled out their census orms. Te Census
Bureau is required by ederal law to protect individuals confdentiality. Tey do so by aggregating
individuals responses within geographic units, collectively known as census geography.
Te smallest piece o census geography is known as a census block. As the name implies, a census
block may be equivalent to a city block in a densely populated urban area. Tey are oen much
larger in rural areas. Tese blocks may be aggregated into block groups and tracts. Te Census
Bureau defnes other geospatial eatures that ollow existing political boundaries, such as county and
state borders. A special type o geography are census places. Te Census Bureau works with states
and their local governments to defne entities that they believe have a distinct identity, which may
depending upon the state include unincorporated areas, villages, townships, towns, cities, and
municipalities. Other spatial data are oen available such as man-made roads and railroads, and
natural eatures such as rivers and lakes.2
INRODUCION
Introduction 6
Map Legend
Block boundaries
Rail Roads
Census places
Bodies of water
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Census population data are supplemented with election data to measure the political consequences
o particular redistricting plans. Minnesota, Ohio, and Wisconsin election data merged to census
data during their redistricting eforts were obtained. For Illinois and Michigan, a database o elec-
tion and census data was constructed.
Several steps are required to merge together census population data and election results. Voting
tabulation districts are larger than census blocks, so the election data must be disaggregated to
this lower level o geography. Te approach used here is to apportion votes to census blocks as a
proportion o a census blocks voting-age population (persons age 18 and older) within each voting
tabulation district. For example, i a census blocks voting-age population constituted 25% o a vot-
ing tabulation district and George W. Bush received 100 votes there, then 25 Bush votes would be
assigned to the census block. Similar approaches were used by data consultants in Minnesota, Ohio
and Wisconsin to produce their redistricting databases.
Te 2000 presidential general election results are analyzed in this report, or two reasons. First,
redistricting authorities oen examine results rom several elections and registration data, as well.
However, in order to make valid comparisons across the ve states, election results or a common
o ce like the presidency must be analyzed. Fortunately, the 2000 presidential election was closely
contested, thus ofering a good measure or districts partisanship.
Second, 1996 and 2004 presidential data might have been examined. However, as a practical matter
o the time and efort o merging together election and census data, analysis was limited to the 2000
presidential general election. Tis is illustrated by the steps taken to merge 2000 election results wit
census population data.
States transmitted their 1998 voting tabulation districts to the Census Bureau. Localities may split o
consolidate their voting tabulation districts rom one election to the next. Tis creates uncertainty
or the correspondence between the voting tabulation districts used in t he 2000 election and censu
blocks. Approximately one percent o Illinois and Michigans 2000 general election voting tabulatio
districts that were split or consolidated between 1998 and 2000 had no clear match to 1998 census
designated voting tabulation districts. In these cases, election results rom the 2000 voting tabulatio
districts were matched with the 1998 voting tabulation districts or unassigned census blocks were
assumed to correspond with an unassigned voting tabulation district. In some cases, particularly
where a new voting tabulation district was ormed in 2000, no inormation was available to assign
the voting tabulation district to census blocks.
Fortunately, the induced error in these cases is typically small since voting patterns in adjacent vot-
ing tabulation districts tend to be similar. Tese assignments are very time consuming because they
require human inspection. Further merging o 1996 and 2004 election data would have likely have
resulted in similar issues.
Matching o election and census data is also incomplete where election absentee ballot results are
reported in separate absentee ballot precincts that have no clear correspondence to census geogra-
phy, such as is the case or Detroit, Michigan. Absentee votes are not assigned to census geography;
however, the error this causes should be small since these states early voting rates in the 2000 elec-
tion were low.
9 Introductio
More up-to-date population data might be desired to orecast the current impact o redistricting
criteria. Unortunately, such population data are not available at the census block level between
censuses. Some data at higher levels o aggregation provide indications o what may happen aer the
next census. Te Census Bureau releases population estimates at the state and county level, which
are used to orecast which states may gain or lose congressional seats through apportionment, which
is the awarding o House o Representative districts to the states based on population as required
by the United States constitution. Tese data also provide clues as to how congressional and state
legislative districts may be arrayed across regions within a state aer the next decennial census.
Starting in 2005, the census long orm the more detailed economic and socio-demographic data
collected rom a sample o American households is now available during redistricting, where
beore it was released aer redistricting. In 2005, the Census Bureau conducted the rst American
Community Survey, also known by its acronym ACS, which is a yearly replacement or the census
long orm. Te Census Bureau distributes the ACS every year to one in a hundred households, as it
did previously or the decennial census long orm. Te ACS includes several important demographic
questions, such as income and education, and relevant or voting rights purposes asks citizenship
status. Te three year average o t he American Community Survey provides statistics down to t he
block group level (collections o blocks) in some areas, but or condentiality reasons these data
cannot be released at the census block level where there may be ew ACS respondents.
Election Data: Tose who draw district lines oen consider their political consequences. o evalu-
ate the political ramications o their actions, they merge together election data with census geogra-phy known as voting tabulation districts, which are townships, precincts or wards, depending on
what a state calls their election units.
As a map o the area around the Wisconsin st ate capital in downtown Madison, Wisconsin demon-
strates, voting tabulation districts are oen composed o several census blocks. Te correspondence
is not by chance. Te Census Bureau works with states to map voting tabulation districts onto
census geography prior to the decennial census during what is known as Phase wo o the census
redistricting data program.4 Tis permits a rather straightorward matching o election and census
data, though there are instances where a census block may be split by a voting tabulation district.
INRODUCION
Introduction 8
Map Legend
Block boundaries
Precinct boundaries
Bodies of water
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Mapping starts with grid plans, where a best attempt is made to draw districts shaped like squares
arrayed on a regular grid. Because states and even census blocks are not always perect squares, ev-
ery district cannot be a perect square. A urther dif culty in drawing nicely-shaped squares is that
the population is unevenly concentrated throughout a state, in sparsely populated rural areas and
heavily populated urban centers. Despite these complications, grid maps are sometimes proposed a
starting points or urther renements on other criteria. Our grid plans serve a similar purpose by
providing map drawing practice in a st ate and identiying areas that may require special attention in
subsequent mapping.
Mapping proceeded next to compact plans. Compactness is a requently cited criterion or reorm
eorts since it is believed that oddly-shaped tentacles and other strangely-shaped non-compact
districts are indicators o political chicanery.
Compactness can be measured in multiple ways, and is oen s aid to be, like beauty, in the eye o th
beholder. Te mapping soware Maptitude generates seven measures o district compactness, which
are described on page 14. Tese measures dier on how they are calculated. A district may be con-
sidered to be compact i it looks like a circle and has ew jagged edges. In some cases, these compac
districts look similar to those drawn or a grid plan, with the exception that districts are allowed
to be taken o a grid so that they might better t together. Districts are drawn with these goals in
mind, rather than trying to maximize a particular compactness measure.
Te next plans drawn minimize the number of county splits. Districts that ollow political bound
aries like counties and other government jurisdictions help keep these communities intact. Arrang
ing districts along existing political boundaries may also help minimize election administration
costs by minimizing the number o jurisdictions that need to hold elections or a district. Districts
that respect county or census place boundaries oen require the creation o ewer voting tabulation
districts and related polling places since voting tabulation districts oen cannot cross district
and existing political boundaries. Crossing a county line might thus create two voting tabulation
districts where only one might otherwise be necessary.
Not all counties can be kept whole. A county with a population that is larger than the ideal popula-
tion size o a district must be split between two or more districts. It is not always possible, either, to
group counties that have populations below the ideal population or a district into a legal popula-
tion- sized district.
Tere are multiple ways to count county splits. Consider a county with three whole or parts o dis-
tricts contained within. Te county might be considered split three times by three districts, or once
by two or more districts. Te rst counting method is used when drawing these test plans, which
counts the number o districts within each county when two or more districts are present and then
sums across all counties. Tis c ounting method produces a higher number o county splits when asingle large-population county has many districts within it, and thereore penalizes a mapping strat
egy that cannibalizes a large county by repeatedly slicing it to round up under-populated districts in
adjacent counties.
Te next plans are those that minimize the number of census place splits . As mentioned previ-
ously, the Census Bureau works with states and their local governments to dene entities that they
believe have a distinct identity, which may depending upon the state include unincorporated
areas, villages, townships, towns, cities, and municipalities. Following these political boundaries
MAPPING SCENARIOS
Grid Plans: Districts that divide a state
into square blocks.
Compact Plans: Districts that create
visually compact districts, often lookinglike circles where possible.
County Splits Plans: Districts that
minimize the number of split counties.
Political Subdivision Plans: Districts
that minimize the number of split census
places, such as townships, cities, and
municipalities.
11 Introductio
HE MAPPING PROCESS
For over a year, rom the all o 2006 and extending through the end o 2007, our research assistants
drew congressional and upper and lower chamber s tate legislative plans or Illinois, Michigan, Min-
nesota, Ohio, and Wisconsin. A computerized commercial mapping program known as Maptitude
was purchased rom the Caliper Corporation at an academic discount and run on our computers
generously provided ree o charge by the George Mason University Geography Department. In all,
over 16,500 individual districts were drawn as part o this mapping project.
Redistricting plans were drawn by our research assistants. Each research assistant was t asked with
drawing a set o plans or each o the three legislative bodies under our criteria scenarios. For all
practical purposes there are nearly an innite number o ways o assigning the hundreds o thou-
sands o census blocks to districts within a state. All district congurations thereore cannot be ex-
plored. However, by analyzing plans drawn by our separate individuals any personal idiosyncrasies
that sneak into an individuals mapping, such as a tendency to always start drawing rom the upper
right corner, will not overly bias this reports ndings.
All districts are commonly drawn under two constraints.
First, districts must be contiguous, that is, they have to internally connect. Districts that connect
at a point, where the only corners o two census blocks touch one another, are not considered to be
connected.
Second, districts must be oequal population. Te ideal population size o a district is computed by
dividing the population o the state by the number o districts. Tere are dierent standards or how
much congressional and state legislative districts may deviate rom the ideal population without
inviting a legal challenge. Legal s cholars generally recognize that congressional districts must deviate
by at most one person rom the ideal in order or a state to avoid a potential ederal legal challenge
to the constitutionality o a states redistricting plan. I a states population is neatly divisible by the
number o congressional districts, the districts must be o absolute equal population. In practice,
drawing such nely-balanced districts is painstaking. It requires hunting and pecking or census
blocks around the perimeter o a district that make its population achieve equality.
o cut down on time costs, a rule was adopted whereby a congressional district could deviate as
much as plus or minus 1% rom the ideal population. Te U.S. Supreme Court is more lenient or
state legislative districts, permitting the population o the largest and smallest districts to deviate by
up to 10% in most instances. A version o this population deviation limit was adopted or our state
legislative districts, requiring that no district deviate by more or less than 5% rom the ideal popula-
tion, although states may impose more strict standards.
Tis report is organized into sections or each o the ve states. An overview o t he state is provided
at the beginning o each state chapter, with a summary o the ndings rom the mapping exercises.
Tese detailed ndings are discussed in three parts, one or congressional districts, one or the
upper state legislative chamber, and one or the lower legislative chamber. At the beginning o each
part, districts adopted or use during the 2000s decade are described and the possibilities or maxi-
mizing the number o minority-majority districts are discussed. Tis is ollowed with a discussion o
the redistricting plans that are drawn under each o our scenarios: grid, compact, minimization o
county splits, and minimization o census place splits.
INRODUCION
Introduction 10
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Compactness: Many ways have been proposed to measure the compactness o districts. Tese man
measures may consider districts perimeter, area, population, or combinations o all three. By one
count, there are over thirty proposed compactness measures. More are be ing proposed all the time.
In act, the number o measures is so great that s ome are occasionally rediscovered.
Te mathematical ormulas or compactness measures can be conusing, s o those wishing to under
stand compactness measures should read this discussion careully.
Compactness measures are ofen named afer the people who rst proposed them. Our mapping
sofware, Maptitude, computes seven o these measures.5 For all but the Perimeter and S chwartzber
tests, the measures range b etween zero and one, with the higher value o one indicating the most
compact district. For these two other measures, a lower value indicates a more compact district.
Many compactness measures compare a districts shape to an idealized circle, since a circle is ofen
regarded as the most compact shape. A circle is the shape with the shortest perimeter that can en-
close a given area. However, like packing marbles in a jar, every district cannot be a circle since the
would be unassigned spaces between districts. Other practical considerations intrude on creating a
ideally compact district. State borders are ofen not regularly shaped, particularly where they ollow
bodies o water. Within states, districts may need to ollow irregularly shaped natural eatures and
man-made eatures, such as city boundaries.
Further detrimental to compactness is that districts must be o equal population. Geographically
smaller districts must be drawn in urban areas. Districts become progressively larger in size as they
are drawn over less densely populated suburban and rural areas. Fitting together these dierent-
sized districts in a compact manner is a challenge. Ofen, oddly-shaped lefover pieces occur in the
transition rom urban to rural areas.
Tese complications are part o the reason why so many compactness measures have been proposed.
Justice Stewarts classic denition o obscenity you know it when you see it has generally been the
guiding principal or identiying when a district is bizarre in shape, to use Justice OConners termi-
nology, rather than dening an explicit mathematical ormula. Our mapping exercise demonstrates
that districts drawn with dierent goals in mind may be considered more compact under some com-
pactness measures compared to others. Tus, it may be inormative to consider multiple compactness
measures when analyzing the compactness o a given district or overall redistricting plan.
Tese compactness measures are best interpreted when comparing redistricting plans within a
given state. Dierent external and internal state boundaries conound between-state comparisons
o compactness. Comparisons o congressional and state legislative districts within states may also
not be entirely comparable since districts may necessarily ollow dierent boundaries due to their
relative sizes.
13 Introductio
Tose wishing to
understand com-
pactness measures
should read this
discussion carefully.
helps keep these communities intact and promotes representation, particularly where oddly shaped
city boundaries result rom ideologically motivated annexation battles. Such districts may, similar to
those that minimize county splits, also help minimize election administration costs. As the preced-
ing example o Springeld, Illinois demonstrates, census places may have strange shapes or imbed-
ded pockets o unincorporated land within their boundaries. A ew census places may even cross
county boundaries. For these plans that minimize census place splits, preerence is given to splitting
counties over splitting census places.
Tese redistricting plans do n ot consider the racial representation goals mandated in the Voting
Rights Act. Racial bloc voting analyses ofen examine patterns o white and minority voting in
several elections to determine levels o racial support or candidates, which is used to determine the
su cient percentage o minorities within a district in order or a minority group to have the op-
portunity to elect a candidate o their choice. Tis project did not have the capacity to conduct racial
bloc voting analyses.
For every legislative chamber examined here, redistricting plans were drawn to maximize the num-
ber o minority-majority districts. In drawing these plans, a minority-majority district is dened as
one with a single minority group comprising a majority o a districts population, Arican-American
or Hispanic. A coalition district, whereby two or more minority groups constitute a majority, does
not count as a minority-majority district.
I the map drawers were able to draw more minority-majority districts than the plan adopted or use
in the 2000s decade, the section describing these adopted districts discusses these options. State-
wide plans that maximize the number o minority-majority districts were not drawn since it is not
clear which criteria should be applied to the districts outside the minority communities. Statistics
or such plans would be contingent on the minority districts and the approaches used to draw other
districts, and thereore may be misleading.
MAP SAISICS
Detailed reports o district-level statistics were generated or each plan. Tere is insu cient space in
this report to report statistics or each plans districts. Such inormation would not truly be inorma-
tive since there would be some 16,500 individual districts to sif through. So, various summary sta-
tistics are provided or all plans drawn under a mapping scenario or congressional, upper chamber
and lower chamber state legislative plans.
Tese plan summary statistics include district measures o the number o county splits, compact-
ness, racial composition, and partisan leanings.
Number of County Splits: Te number o counties split by districts is counted as the sum o the
number o districts within each county, or all counties with more than one district. For example,
i a county contains two districts, whole or in part, then it is split twice. A county or collection o
counties with one district are not counted as being split. Te average number o county splits across
all plans o a given plan type is reported.
INRODUCION
Introduction 12
Tese redistrict-
ing plans do not
consider the racial
representation goals
mandated in the
Voting Rights Act.
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Te Schwartzberg Measure
Te Schwartzberg Measure has three steps and tries not to penalize districts that
have odd shapes due to natural eatures or political boundaries. In the frst step, a
simplifed version o the district is created that eectively excludes odd peripheral
eatures due to water or an adjoining state, or example. In the second step, the
perimeter o a circle with the same area as the simplifed district is computed. In
the third step, the ratio o the perimeter o the simplifed district to the perimeter
o the circle is computed. Tis measure tends to penalize districts with one or mor
tentacles or with many jagged edges, but does not penalize a district i the jagged
edges are a consequence o external boundaries.
For the Schwartzberg measure, a smaller number indicates a more compact
district. A perectly compact district scores as one and larger numbers as less
compact. (Te average Schwartzberg test score or all districts is reported or each
map type.)
Te Population Circle Measure
Te Population Circle Measure, like the Roeck measure, draws the smallest pos-
sible circle around a district. Instead o comparing areas, the measure is the ratio
o a districts populations to that o the enclosing circle. Tis measure thereore
does not penalize districts heavily or ailing to include peripheral territory that
has little or no population, such as water. Districts drawn around population cen-
ters tend to are well using this measure.
Te Population Circle measure varies between zero and one. Larger numbers
indicate a more compact district. (Te average Population Circle measure or all
districts is reported or each map type.)
Te Population Polygon Measure
Te Population Polygon Measure is similar to the Population Circle test in that
its primary consideration is population rather than area. Instead o a circle drawn
around a district, the minimum convex enclosing shape (i.e., it cannot bow
inwards) is drawn around the district. Te ratio o a districts population to thisconvex polygon is then computed.
Te Population Polygon measure varies between zero and one. Larger numbers
indicate a more compact district. (Te average Population Polygon measure or al
districts is reported or each map type.)
15 Introductio
Te Perimeter Measure
Te Perimeter Measure is perhaps the simplest o all compactness measures. It is
simply the length o a districts perimeter. Districts with relatively straight edges
tend to score as more compact by this measure while those with jagged edges tend
to have longer perimeters.
Te Perimeter Measure ranges rom zero to infnity. A smaller number indicates
a more compact district. (Te average sum o all district perimeters is reported or
each map type.)
Te Roeck Measure
Te Roeck Measure is the ratio o a districts area to that o the s mallest circle that
can be drawn to enclose the entire district. Tis test penalizes districts that may
have one or more tentacles reaching rom the district core.
Te Roeck measure varies between zero and one. Larger numbers indicate a
more compact district. (Te average Roeck measure or all districts is reported or
each map type.)
Te Ehrenburg Measure
Te Ehrenburg Measure is the ratio o the area o the largest circle that can be
drawn inside a district to area o the district. Tis test penalizes districts that may
have one or more tentacles reaching rom the district core.
Te Ehrenburg measure varies between zero and one. Larger numbers indicate a
more compact district. (Te average Ehrenburg measure or all districts is reported
or each map type.)
Te Polsby-Popper Measure
Te Polsby-Popper Measure has two steps. In the frst step, the area o circle with
the same perimeter length as the district is computed. In the second step, the ratioo the area o the district to the area o the circle is computed. Tis measure tends
to penalize districts with one or more tentacles or with many jagged edges.
Te Polsby-Popper measure varies between zero and one. Larger numbers
indicate a more compact district. (Te average Polsby-Popper measure score or all
districts is reported or each map type.)
INRODUCION
Introduction 14
Our seven compactness measures are as follows:
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17 Introductio
Tis report is organized into fve color-coded chapters or each o
the fve Midwestern states oIllinois, Michigan, Minnesota, Ohio
and Wisconsin. An overview o the state is provided at the beginning
o each state chapter, along with a summary o the fndings rom the
mapping exercises. Te detailed mapping exercises are discussed in
three parts, one or congressional districts, one or the upper state
legislative chamber, and one or the lower legislative chamber. At the
beginning o each part, districts adopted or use during the 2000s
decade are described and the possibilities or maximizing the num-
ber o minority-majority districts are discussed. Tis is ollowed
with a discussion o the redistricting plans that are drawn under
each o our scenarios: grid, compact, minimization o county splits,
and minimization o census place splits. Please reer to the Introduc
tion or more details.
Number of majority-minority districts: Te Census Bureau reports the number o persons by race
and their Hispanic origin. Racial classifcations are complicated on the 2000 census because people
were permitted to identiy themselves by multiple racial categories. In addition to race, the Census
Bureau asks whether or not a person is o Hispanic origin. wo racial/ethnic categories are thus
defned. One is Arican-American, which includes any person who identifed themselves as
Arican-American alone or in combination with another racial or ethnic category. Te other is
Hispanic, which includes any person who identifed their ethnicity as Hispanic. It is important to
note that the two are not mutually exclusive, that is, some people identiy themselves as Hispanic
Arican-Americans.
Te average number o Arican-American and Hispanic majority districts are reported o across all
plans o a given plan type.
Political Composition: A districts partisan leaning is measured by the closely contested 2000
presidential election, which is the election most proximate to the post-2000 census redistricting in
these fve states. o measure the political composition o districts the presidential election results are
slightly modifed. Following standard practice among academics who study elections, minor party
candidate votes are actored out by calculating the two-party vote, the vote shares o the two major
political parties. Tis is not to say t hat these minor party candidates are unimportant, rather, in typi-
cal redistricting how districts are sculpted to avor major party candidates is most interesting.
Four types o districts are classifed:
Strong Republican is where the two-party vote is above 55% pro-Republican perormance.
Competitive Republican is where the two-party vote is between 50-55% pro-Republican perormance.
Competitive Democratic is where the two-party vote is between 50-55% pro-Democratic perormance.
Strong Democratic is where the two-party vote is above 55% pro-Democratic perormance.
Te breakpoints between sae and competitive districts are somewhat arbitrary. A competitive
district with 54.9% pro-Democratic perormance is only slightly more competitive than a strong
Democratic district with 55.1% pro-Democratic perormance. Furthermore, more accurately stating
districts competitiveness requires a statistical analysis o election results over a longer period o
time that is outside the scope o this project.
It is also important to note that district competitiveness is just one actor in an election outcome.
While the playing feld may be tilted towards one o the two candidates because o the relative
numbers o Democrats and Republicans within a district, the candidates campaigns also matter.Election winners are shaped by the presence o an incumbent, the experience o a challenger, money,
campaign message, national mood, scandal, and much more. A districts partisanship is simply one
among many actors that inuence election outcomes, but it is one o the ew t hat incumbents have
direct control over.
Te average number o sae and competitive Democratic and Republican districts are reported o
across all plans o a given plan type.
INRODUCION
Introduction 16
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Illinois 18
Illinois Political Subdivisions
Kaskaskia, Illinois
Census Places Around Cook County
Te Land o Lincoln is located in the northern center o the
continental United States. Lake Michigan orms the border
along the states northeast corner. Wisconsin borders the state
to the north in a straight east-west line at 42 30 north latitude
established when the state was carved rom the Illinois erritory
in 1818 at the urgings o Nathaniel Pope, the Illinois erritory
delegate to the U.S. Congress. Previously, Illinois territorial
border established under the Northwest Ordinance o 1787
was approximately 30 miles southward and did not include
access to Lake Michigan, where present day Chicago is located.
Te Mississippi River constitutes the western border, the
Ohio River the southern border, and the Wabash River the
southern hal o the eastern border. Te northern hal o the
eastern border was fxed at 87 31 30 longitude when the
state o Illinois was ormed.
Political Subdivisions: Illinois has 102 counties. Te Census
Bureau, working with the state, defnes 1,313 census places,
which in Illinois are the cities, towns, villages, and, in a ew
cases, unincorporated communities that are thought to have
distinct identities. Tese range rom Kaskaskia, the smallest
with a 2000 census total population o nine persons. (Te village
o Ohlmans initial count o zero persons was later revised to
148.) Kaskaskia is the original capital o the Illinois erritory
and state o Illinois, beore the capital was moved to Vandalia in
1820. Te village was destroyed by an 1881 ood that carved a
new channel in the Mississippi River and placed Kaskaskia on the western bank o the Mississippi.
Tus, Kaskaskia is a part o Illinois located on the west bank o the Mississippi River. Kaskaskias
history illustrates that irregularly shaped waterways aect the states external and internal political
boundaries. For example, another major river o note that orms many county borders is the Illinois
River, which winds its way through the north central portion o the state rom Chicago to just north
o St. Louis.
Te largest census place in Illinois is Chicago, with a population o 2,896,016. O course, many
people live in the suburban cities nestled around Chicago. Te metropolitan area o Cook County,
the home o Chicago, together with the Collar Counties o DuPage, Kane, McHenry, and Will
contains 8,091,720 persons or 65% o the states entire population according to the 2000 census.
Te map o Cook County and its surrounding Collar Counties demonstrates how census places aredensely packed around the Chicago area. A close inspection also reveals how a number o these
census places straddle county lines. Districts that place a preerence on maintaining the integrity o
census place or county borders will thus necessarily have dierent confgurations.
Legend
Counties
Census places
Bodies of water
Illinois
19 Illino
Illinois Quick Facts
No. of Counties:
No. of Census Places:
Population 2000 Census
Total Population:
Non-Hispanic White:
% Non-Hispanic White
African-American:
% African-American
Hispanic:
(incl. Hispanic African-Amer% Hispanic
2000 Election Total Votes
George Bush:
Al Gore:
% Bush of Bush & Gore Vote
COOKDUPAGE
LAKE
WILL
KANE
WINNEBAGO MCHENRY
MADISON
ST. CLAIR
SANGAMON
PEORIA
CHAMPAIGN
MCLEAN
ROCK ISLAND
TAZEWELL
MACON
LA SALLE
KANKAKEE
DEKALB
VERMILION
ADAMS
WILLIAMSON
WHITESIDE
JACKSON
KNOX
KENDALL
COLES
OGLE
HENRY
MACOUPIN
STEPHENSON BOONE
MARION
JEFFERSON
LIVINGSTON
FRANKLIN
FULTON
GRUNDY
MORGAN
LEE
CLINTON
BUREAU
WOODFORD
CHRISTIAN
EFFINGHAM
RANDOLPH
MCDONOUGH
IROQUOIS
LOGAN
MONTGOMERY
MONROE
SALINE
PERRY
SHELBY
JO DAVIESS
FAYETTE
JERSEY
CRAWFORD
HANCOCK
DOUGLAS
EDGAR
WARREN
UNION
BOND
PIKE
WAYNE
CLARK
MERCER
DEWITT
CARROLL
PIATT
RICHLAND
MASON
LAWRENCE
WHITE
MASSAC
WASHINGTON
GREENE
CLAY
MOULTRIE
FORD
CASS
MARSHALL
WABASH
JOHNSON
MENARD
CUMBERLAND
JASPER
ALEXANDER
HAMILTON
HENDERSON
PULASKI
SCHUYLER
EDWARDS
BROWN
GALLATIN
STARK
PUTNAM
SCOTT
CALHOUN
HARDIN
POPE
Chicago
Rockford
Aurora
Peoria
Springfield
Joliet
Waukegan
Decatur
Champaign
Bloomington
Rock Island
East St. Louis
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Illinois 20 21 Illino
Summary o est Redistricting Plans
In the test plans that ollow, Illinois redistricting is shown to be dominated by Chicago and its Collar Countie
where more than hal o the states population resides and where more than hal o the states districts be it
congressional or state legislative must be drawn. Te inner core o Chicago is heavily Democratic and the
metropolitan area becomes progressively more Republican in the surrounding suburbs.
Te high concentration o Democrats into urban Chicago means that Democrats are not ef ciently distribute
throughout the state or redistricting purposes. Even though Illinois voters cast more votes or Gore, Repub-
licans are markedly better than their statewide perormance in nearly all test plans. In some cases a majority
o the districts even avor Republicans. Plans that segregate the city o Chicago or Cook County in particular
overly concentrate Democrats into districts that they win overwhelmingly, while Republicans constitute a
narrow majority in a larger number o districts. For Democrats to receive a share o districts proportional to
their share o the statewide vote, districts need to cross Cook Countys lines to create more districts avorable
to Democrats.
Interestingly, the Republican advantage in redistricting is mitigated as districts become smaller. Tis is perhap
somewhat o a surprise since these smaller districts are less capable o addressing inef cient over-concentra-
tion o Democrats in the Chicago area by drawing districts that tie together the Democratic city core with
the Republican suburbs. For the legislative districts, particularly the House districts, the challenge to overall
representation reective o the state posed by the Chicago area can be oset by consolidating Downstate citie
into districts that avor Democrats. As a result, our test mapping o the House districts consistently best reec
the overall political composition o the state.
Te states minority populations are largely concentrated within the Chicago area, and while they are some-
what compact, they do not always neatly t into the most compact districts. Districts that do not explicitly
take race into account may produce some minority districts, but not as much as the 2000s plans that aspire to
promote racial representation. Our test plans suggest that ollowing these criteria examined here are insuf -
cient to adhere to ederal Voting Rights requirements.
Population: Te red scar in the upper right corner o the Illinois population density map represents
the high concentration o people living in Chicago and the Collar Counties. Notable mid-sized
larger cities and communities dot Downstate, too. For example, Peoria has 112,936 persons;
Springeld has 111,454 persons; Champaign/Urbana has 103,913; Decatur has 81,860; Rock Island
County with the city o the same name has 149,374; and the Counties o Madison and St. Clair
(which include the city o East St. Louis) have a combined total o 515,023 persons.
Te equal population requirement or legislative districts means that more than hal o t he states
districts must be located in and around the Chicago area, and about a h must be drawn around
the East St. Louis area. In both areas, small districts must be drawn in the urban interior and pro-
gressively larger districts must be drawn in the less densely populated suburban and outlying rural
areas. For the other mid-sized cities, the choice whether to consolidate these cities into one or more
urban districts or to split them among districts with an urban and rural mix may aect the character
o their representation and the overall balance o Democrats and Republicans in the congressional
delegation and state legislature.
Illinois is a racially mixed state. A little over two-thirds o the states population is non-Hispanic
White. Fieen percent o the states population is Arican-American and twelve percent is Hispanic.
Te states minority populations tend to be concentrated within urban areas, particularly Chicago
and East St. Louis. Tere are minority communities in the mid-sized cities and s cattered throughout
the rural areas, but according to the 2000 census, these communities tend to be too dispersed to
enable the drawing o minority-majority districts except in the East St. Louis area.
Politics: Illinois is divided like other states into Democratic urban areas and Republican rural areas.
Concentrations o Democrats Downstate, particularly in the mid-sized cities and in the East St.
Louis area, can support Democratic leaning districts. However, the partisan composition o the state
is dominated by the large number o Democrats living in Chicago and its environs. As a consequence,
Bush only received 43.8% o the combined Bush and Gore vote in 2000, the metric used to analyze
the partisan composition o districts in this report.
Perhaps surprisingly, Republicans enjoyed majority control o the state Senate during the 1990s, and
the state House until 1996. Redistricting is a key part o Republicans success in the 1990s. Republicans
drew state legislative lines in the 1990s and employed a strategy o splitting downstate cities and
drawing Republican leaning districts in the Collar Counties that took in just enough Democrats
to waste their votes in districts Republicans would win. Te Democrats controlled the process in
2000, and not surprisingly, devised state legislative plans with the opposite strategy in mind o
consolidating Downstate cities and splitting Republican areas to waste their votes. Democrats have
dominated the state legislature in the 2000s. Tus, as the shiing ortunes o the parties illustrate,
who draws the lines and how they are drawn can be an important actor in who controls the Illinoisstate government.
Illinois Population Density
Illinois Racial Diversity
Illinois Partisan Support
Less Dense
More Dense
Less
Minorities
More
Minorities
More
Bush Votes
More
Gore Votes
ILLINOIS
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Illinois 22
Map Legend
District boundaries
Counties
Census places
Bodies of water
23 Illino
4th
Congressional 2000s Map
Congressional 2000s Map Chicago detail
Statistics
Statistics for 2000s Plan
Number of Districts: 19
County Splits: 49.0
Compactness Measures
Roeck: 0.335
Schwartzberg: 2.457
Total Perimeter: 6965.1
Polsby-Popper: 0.201
Population Polygon: 0.629
Population Circle: 0.382
Ehrenburg: 0.308
Racial Composition
African-American Majority Districts: 3
Hispanic Majority Districts: 1
Partisan Composition
Strong Republican: 7
Lean Republican: 2
Lean Democratic: 3
Strong Democratic: 7
Descriptions of map statistics provided on page 12.
15
17
7
4
ILLINOIS CONGRESS
Te Illinois constitution and state statutes are silent on the
congressional redistricting process and the criteria that should
be applied to drawing congressional districts. Te state thus
uses the regular legislative process the same process used to
create typical laws to draw congressional districts. Te state
ollows ederal criteria that congressional districts must be
single-member, o equal population, and adhere to the ederal
Voting Rights Act.
A divided state legislature elected in 2000 created the environ-
ment or a bipartisan compromise on redistricting. At the
time, Democrats controlled the st ate House, Republicans
controlled the state Senate, and Republican George Ryan was
governor. Te states loss o a congressional seat to reapportion-
ment urther complicated redistricting and likely meant two
incumbents would race of in a primary or general election.
Chicago area Rep. Rod Blagojevichs decision to run or
governor might have provided a compromise opportunity, but
the states population loss came rom Downstate, which meant
a congressional district must be collapsed in that region.
Rather than ace an uncertain court battle, then-Republican
U.S. House Speaker Dennis Hastert and Democratic Rep. Bill
Lipinski orged a bipartisan compromise.1 While congress
members do not play a ormal role in redistricting, states oen
adopt districts proposed by them.2 Tis compromise plan was
adopted by the state government.
Te plans contorted districts would warm the heart o Gov.
Elbridge Gerry, the namesake o the gerrymander. Republicans
had a perceived upper hand in negotiations because a ederal
court had chosen a Republican plan in the 1990s when the
divided state government deadlocked. Legislators anticipated
a similar outcome and believed another Republican riendly
court would draw districts i a compromise could not be
reached.3 Te heavy ax ell on Downstate Democratic Rep.
David Phelps. Te tornado-shaped 15th congressional district
on the states eastern edge was designed to deny him reelec-tion. Te end o the unnel touches down in Eldorado, where
Phelps home can be ound. o urthe r make it di cult or
him to move his residence into a riendlier district, much o
his then-current district was dismantled into three districts.
Te crab-shaped 17th district represented by Democrat Rep.
Lane Evans was congured to consolidate as many Downstate
Democrats as possible into a single district, urther hobbling
Phelps opportunities. Te southern pincer o the crab cuts
a block-wide path through parks and shopping malls in
Springeld to grab a minority community on the eastern edge
o town and union areas o Decatur to the east. Phelps moved
into the 19th congressional district, which comprised 34%
o his old district, to run against Republican incumbent Rep.
John Shimkus and lost.4
From aar, the 15th and 17th districts are two o the seemingly
most contorted congressional districts, but peering into
Chicago reveals the ear-muf shaped 4th congressional district
that is oen used as an example o gerrymandering. Tere is a
legitimate representational rational or this district, as it con-
nects together two Hispanic communities that are s eparated
by an Arican-American community located in the 7th dis-
trict. Te 4th congressional district was created in the 1990s by
a ederal court which ound that these Hispanic communities
merited an opportunity to elect a candidate o their choice per
Section 2 o the Voting Rights Act.5
American history is embedded in t his plan, too. Democratic
Representative Bobby Rush, representing the 1st congressional
district on Chicagos Southside, had his primary challenger in
the 2000 election removed rom the district. A young Illinois
state Senator named Barack Obama then decided to run or
U.S. Senate rather than challenge his new representative,
Democrat Jessie Jackson, Jr.. Obamas home was just a ew
blocks rom Rushs new district and he was just one among
three potential challengers who ound themselves removed
rom Rushs district.6
Given its irregularly-shaped districts, it is perhaps not surprising
that the redistricting plan splits 49 counties and scores low
on nearly all compactness measures. Tere are three Arican-
American majority districts and one Hispanic majority
district, all ound in the Chicago area. Surprisingly, in this
strongly Democratic state, Gore received a majority vote inonly ten o nineteen 2000s congressional districts, and was
represented by ten Republicans and nine Democrats in 2002,
the election ollowing the redistricting.7 Only ve o these
districts are within a competitive range: two Republican and
three Democratic.
Congressional 2000s Plan
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Illinois 24
Map Legend
District boundaries
Counties
Census places
Bodies of water
25 Illino
Congressional Grid Test Map 1
Congressional Grid Test Map 2
Statistics
Averages for 3 Test Plans
No. of Districts: 19
County Splits: 54.0
Compactness Measures
Roeck: 0.517
Schwartzberg: 1.315
Total Perimeter: 3910.8
Polsby-Popper: 0.561
Population Polygon: 0.920
Population Circle: 0.548
Ehrenburg: 0.534
Racial Composition
African-American Majority Districts: 1.3
Hispanic Majority Districts: 0.0
Partisan Composition
Strong Republican: 4.0
Lean Republican: 5.3
Lean Democratic: 2.7
Strong Democratic: 7.0
Descriptions of map statistics provided on page 12.
ILLINOIS CONGRESS
Tree grid plans are drawn where districts are designed to best
approximate squares. Each congressional district cannot have
the same uniorm square shape because the states borders are
not straight-edges. Te distribution o people across the state
urther challenges the drawing o straight lines. More districts
must be drawn within the densely populated Chicago area in
order to equalize districts population. Te state is also longer
in a north-south direction than it is wide in an east-west
direction, and in the Downstate region population is concen-
trated along the states western border, thereby requiring more
districts along the states Downstate western border.
Te two maps to the right illustrate two approaches to drawing
grid plans in Illinois. In the example map to the upper right,
the state is bisected down the middle, except or the northern-
most district. Te map on the lower right approaches the divi-
sion o the state by frst drawing a district that incorporates the
southern-most part o the state into a district and proceeds
northward. In both confgurations, note how the greater popu-
lation density in the western portion o Downstate permits
districts to be stacked one upon the other along the western
border, while the eastern districts south o Chicago must
encompass a larger area. In both examples, the eastern Down-
state districts tend to be longer in a north-south direction than
those to the west.
Te Chicago areas highest concentration o population along
Lake Michigan lends itsel to the ormation o three districts
stacked along the coast. Larger districts in the lesser, though
still highly populous, outlying suburbs ring these central city
districts. Tese outer districts cannot orm nicely-shaped
squares. Te map on the upper right tries to retain a square
shape or every district while the map below tries to create
more square shaped districts, while sacrifcing one districts
square shape by using it to accumulate leover pieces.
Compared to the 2000s plan, these grid plans have on averagea greater number o county splits than the plan employed in
the 2000s. Straight-edge census blocks that ollow armland
and east-west or north-south roads in t he Downstate region
are used as district borders. Tese roads tend to make straighter
district borders than the s ometimes-irregular county lines
composed o rivers. As might also be expected, these districts
score highly compact on multiple compactness measures and
are more compact than the 2000s plan.
Tese plans do not t ake into account the Voting Rights Act.
On average they have 1.3 Arican-American majority districts
and none had a Hispanic-majority district. Te minority
communities in the central Chicago area are large enough and
compact enough to draw at least one-Arican-American dis-
trict, but urther districts are limited. Arican-American com-
munities extend rom Southside Chicago, one to the northwest
and one to the southwest. Along Lake Michigans shore to the
north o Southside Chicago are Whites who live in high-rise
apartments. Tus, square districts that use Lake Michigan as
an eastern boundary will necessarily combine minority and
non-minority communities. Tese congressional grid plans
also ail to create a Hispanic-majority district because the
Hispanic communities are not as concentrated as the Arican-
American communities and thus some consideration o race
must enter into the drawing o a Hispanic-majority district.
Politically, these three grid plans look on average similar to
the 2000s plan. Tere are on average 9.7 Democratic and 9.3
Republican majority districts. A dierence emerges among the
districts in the competitive range. Where these grid plans have
an average o 8.0 competitive districts, 2.7 Democratic and 5.3
Republican, the 2000s plan only has 5 competitive districts,
3 Democratic and 2 Republican. Tese competitive numbers
help explain why despite being a heavily Democratic state the
Republicans have near parity in these grid plans. Democrats
are concentrated into the central Chicago area and congres-
sional districts that emphasize compact shapes, such as these
grid plans, concentrate Democrats into uncompetitive central
Chicago districts. Te remainder o the state has a more even
political balance, slightly tilting towards Republicans, which
overall results in a more e cient distri bution o Republicans
into districts across the state.
Congressional Grid
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Illinois 26
Map Legend
District boundaries
Counties
Census places
Bodies of water
27 Illino
Congressional Compact Test Map 1
Congressional Compact Test Map 2
Statistics
Averages for 3 Test Plans
No. of Districts: 19
County Splits: 45.0
Compactness Measures
Roeck: 0.526
Schwartzberg: 1.362
Total Perimeter: 3991.9
Polsby-Popper: 0.533
Population Polygon: 0.891
Population Circle: 0.567
Ehrenburg: 0.556
Racial Composition
African-American Majority Districts: 1.0
Hispanic Majority Districts: 0.0
Partisan Composition
Strong Republican: 3.7
Lean Republican: 6.0
Lean Democratic: 2.7
Strong Democratic: 6.7
Descriptions of map statistics provided on page 12.
ILLINOIS CONGRESS
Tree compact Illinois congressional plans are drawn, which
attempt, where possible, to draw districts that may be circular
or square, but are not constrained to all on a grid. In most
rural areas, Illinois county boundaries tend to orm straight
lines and even tend to do so or census blocks laid over the
armland. In Chicago, city blocks tend also to be straight-
edged as well, generally ollowing streets uninterrupted in
north-south and east-west directions. Tese grid-like patterns
aid drawing square districts. Circular districts, however, tend
to have ragged, pixilated edges because census blocks do not
have rounded borders, and thus surprisingly are poorly on
compactness measures that avor smaller district perimeters.
Te rounded path o the Mississippi River, combined with the
population center around East St. Louis, aids the drawing o cir-
cular congressional districts in this region. In the e xample map
to the upper right, there is a district with a core encompassing
Madison and St. Claire Counties. o the north, the Mississippi
River ortuitously bends westward with just enough space and
population to orm another circular-like district.
A good strategy could not be devised to draw circular districts
in the Chicago area. Te Lake Michigan coast ollows a nearly
straight line to the north-north-west and thus orms a regular
border that will necessarily cut any circular district. he
districts in the map to the lower right look similar to grid dis-
tricts, though the districts have been rearranged so that they
are more tightly packed together without generating as many
excess lefover pieces.
On average, these compact plans split 45 counties, which is
ewer than our grid plans and the 2000s plan. Cook County
and the Collar Counties must be split due to the numerous
districts that must be drawn in this region, so reductions in
county splits must be realized in Downstate districts. Tese
compact plans generally ollow county lines where they can,
though perhaps urther improvements in compactness could
have been realized by shaving some county corners.
On average, our compact plans had only one Arican-American
majority district and no Hispanic majority districts. As discussed
with regards to the grid plans, the minority population in
Chicago, while concentrated into the city core, is not arrayed
in a manner that acilitates their inclusion into more than
one district that maximizes compactness. Tis suggests that a
compactne ss standard is insu cient to satis y ederal Voting
Rights Act requirements.
Our three compact plans are, on average, politically similar to
our grid plans and the 2000s plan. Tere are on average 9.4
Democratic and 9.7 Republican majority districts. O these,
2.7 Democratic and 6.0 Republican districts are in a competi-
tive range. Te same dynamic aects the partisanship o the
grid and compact plans. Democrats are concentrated within
the Chicago regio n while Republicans are more e ciently
distributed Downstate to give them an advantage in redistrict-
ing over what might be expected given the states substantial
Democratic tendencies.
Congressional Compact
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Illinois 28
Map Legend
District boundaries
Counties
Census places
Bodies of water
29 Illino
Congressional Minimize County Splits Test Map 1
Congressional Minimize County Splits Test Map 2
Statistics
Averages for 3 Test Plans
No. of Districts: 19
County Splits: 14.0
Compactness Measures
Roeck: 0.425
Schwartzberg: 1.611
Total Perimeter: 5098.1
Polsby-Popper: 0.398
Population Polygon: 0.789
Population Circle: 0.472
Ehrenburg: 0.416
Racial Composition
African-American Majority Districts: 0.7
Hispanic Majority Districts: 0.0
Partisan Composition
Strong Republican: 5.0
Lean Republican: 5.3
Lean Democratic: 1.7
Strong Democratic: 7.0
Descriptions of map statistics provided on page 12.
ILLINOIS CONGRESS
Tree congressional plans that minimize the number o county
splits are drawn. Such plans ofen present interesting puzzles
to solve since there are only a limited number o ways in
which districts can be congured such that they cross county
boundaries the ewest times possible. In a county such as
Cook where multiple districts may be drawn, districts are
generally drawn to be compact within the countys borders.
A place to begin solving this puzzle is to consider counties that
can hold one or more entire districts without crossing
the county line. Te ideal population or one o Illinois 19
congressional districts is 653,647 persons, which we permit
to deviate by 1% or 6,536 persons in our test plans. 8 Cook
Countys 5,376,741 persons supports 8.2 congressional
districts, which is just a little too much population to pack in 8
over-populated districts and retain a 1% population deviation.
Lake County, to the north o Cook County, has a population
o 644,356, which is just under the ideal population to sup-
port a single district within a 1% population deviation. Tus,
a natural division between these two counties is to cross the
county line once to round o the population o a Lake County
district. DuPage Countys population o 904,161 supports 1.4
districts and must be split. Te most logical choice is to round
o the population o a second district with Kane County to
the west, which has a population o 404,119. Te remaining
Kane County population can be combined with other counties
to orm another district.
Surprisingly, the remaining counties happen to have just the
right number o persons to draw the remaining districts in
the state without splitting another county. Indeed, as the two
maps to the right show, there are even dierent congurations
o Downstate districts that do not split another county.
Tere are an average o 0.7 Arican-American majority
districts and zero Hispanic districts among these three plans.
Minority communities extend slightly rom Cook County
into DuPage and Will Counties, thus minimizing county
splits does not necessarily place a constraint on the number
o minority districts. A conguration o eight Cook County
districts with the same number o minority-majority districts
as the 2000s plan, 3 Arican-American and 1 Hispanic, is
perhaps easible i a map drawer took race explicitly into
account in drawing internal Cook County districts, as may
be required by the ederal Voting Rights Act.
Tese plans that minimize the number o county splits are
slightly more avorable towards the Republicans than the
2000s plan and the grid and compact test plans. On average,
Republicans constitute a majority in 10.3 districts and Demo-
crats 8.7. Among these districts, 5.3 are Republican-leaning
competitive and 1.7 are Democratic-leaning competitive. In
these plans, the imperative to respect the boundaries o Cook
County even more strongly segregates Democrats into heavily
Democratic districts. In the remainder o the state, one o our
Downstate congurations split the concentration o Demo-
crats in the East St. Louis communities o Madison and St.
Clair Counties, resulting in one ewer Democratic district.
Te result rom respecting county lines is that Republicans are
more e ciently distributed into districts than the Democrats,
who nd many o their supporters clustered in heavily Demo-
cratic Chicago area districts.
Congressional Minimize County Splits
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Illinois 30
Map Legend
District boundaries
Counties
Census places
Bodies of water
31 Illino
Congressional Minimize Census Place Splits Test Map 1
Congressional Minimize Census Place Splits Test Map 2
Statistics
Averages for 3 Test Plans
No. of Districts: 19
County Splits: 58.7
Compactness Measures
Roeck: 0.452
Schwartzberg: 1.795
Total Perimeter: 5055.1
Polsby-Popper: 0.306
Population Polygon: 0.797
Population Circle: 0.495
Ehrenburg: 0.414
Racial Composition
African-American Majority Districts: 1.0
Hispanic Majority Districts: 0.0
Partisan Composition
Strong Republican: 3.0
Lean Republican: 6.0
Lean Democratic: 3.0
Strong Democratic: 7.0
Descriptions of map statistics provided on page 12.
ILLINOIS CONGRESS
Tree plans that minimize the number o split census places
are drawn, which are Census Bureau designations o city,
town, village, and other community borders created in con-
sultation with the Illinois state government. Te approach is
similar to our plans that minimize county splits, except that
the boundaries o the smaller census places are respected,
which sometimes even straddle county lines. Districts internal
to census places, such as Chicago, are generally drawn to be
compact within census places borders.
A major diference in the mapping approaches is evident in
the Chicago area. Te city o Chicagos population o 2,896,016
persons supports 4.4 congressional districts. Tus, at least
one district must straddle the citys border. Te many smaller
suburban cities ringing Chicago and pockets o unincorporated
county geography have just the right population to make it
possible to split only this one census place in the entire state.
Te map to the upper right demonstrates one such congurat