Making Graphs

The Basics … Graphical Displays Should:

• induce the viewer to think about the substance rather than about the methodology, graphic design, the technology of the graphic production, or something else

• avoid distorting what the data have to say

• present many numbers in a small space

Continued...

The Basics … Graphical Displays Should: (2)

• make large data sets coherent

• encourage the eye to compare different pieces of data

• serve a clear purpose

• be closely integrated with the statistical and verbal descriptions of a data set.

Lie Factor

• Lie Factor = size of effect shown in graphic

size of effect in data

• Greater than 1.05% or less than .95% indicates substantial distortion, far beyond minor inaccuracies in plotting.

NYT: Fuil economy “graph”

The eye perceives area, not height

Maps: just bad graphs

Maps: just bad graphs

Maps: just bad graphs

Maps: just bad graphs

Maps: just bad graphs

Maps: just bad graphs

Maps: just bad graphs

Chartjunk

• What is it? Anything that doesn’t NEED to be included in the chart.

• To clean-up chartjunk, watch your data-ink ratio. “Data-ink is the non-erasable core of a graphic, the non-redundant ink arranged in response to a variation in the numbers represented.”

Data-ink ratio = data-ink

total ink used to print the graphic

Some cool historical graphs1. Planetary orbits, 10th or 11th century

William Playfair (1759-1823)

Inventor of:

• Line graph

• Bar graph

• Pie chart

Trade balance of England

Imports and exports of Scotland

Playfair: area of countries (circles), population (left line seg.) and tax revenue

(right line seg.).

U.S. age pyramids, 1874

Minard's Napoleon's March to Moscow

Tufte principles:

• Show Data• Focus on Content instead of graphic production

• Avoid Distorting what Data has to say

• Make Large Data Sets Coherent• Encourage Eye to Compare Different Pieces

of Data• Reveal Data at several Levels of Detail• Closely integrate Statistical and Verbal

Descriptions

• Line Graph – x-axis requires quantitative variable– Variables have contiguous values– familiar/conventional ordering among ordinals

• Bar Graph– comparison of relative point values

• Scatter Plot– convey overall impression of relationship between two

variables• Pie Chart

– Emphasizing differences in proportion among a few numbers

Bar charts

• Best for comparing different things during the same time period

• Neither the bars nor the axis should be interrupted

• Axis should usually include zero (some exceptions)

• Avoid 3-D effects, can be misleading

Line graphs

• Best for showing change over time

• Can indicate trends

• Use a different color and symbol for each line

• Avoid too many lines

• When to use log scale

0

10

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1850 1870 1890 1910 1930 1950 1970 1990

Census year

Pe

rce

nt

wit

h c

hil

dre

n

White

Black

Percent of Persons Aged 65+ Residing with their Own Children aged 18+:

United States 1850-2000

Labeling: Title

Height/width should be about 3:4 (same as old-fashioned TV

Labeling: lines

Percent of the Labor Force Employed in Agriculture, United States, 1800-2000

0

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20

30

40

50

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1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000

Year

Pe

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Figure 1: Percent of elders in intergenerational families

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30

40

50

60

70

1970 1975 1980 1985 1990 1995 2000

Per

cent

Argentina

Brazil

Chile

Colombia

Costa Rica

Ecuador

Kenya

Mexico

Philippines

Romania

Rwanda

Vietnam

South Africa

Uganda

Venezuela

Too many lines!

0

5

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20

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30

35

40

45

50

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Pe

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nt

in L

ab

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Fo

rce

MexicoMexicoCosta RicaCosta Rica

EcuadorEcuador

ChileChile

VenezuelaVenezuela

ColombiaColombia

BrazilBrazil

Married Female Labor Force Participation in Latin America(age 18 to 65)

0

10

20

30

40

50

60

70

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Pe

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nt

in L

ab

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rce

Latin Latin AmericaAmerica

United United StatesStates

Married Female Labor Force Participation:Latin America and U.S. (age 18 to 65)

0

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20

30

40

50

60

70

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Pe

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in L

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United United StatesStates

MexicoMexicoCosta RicaCosta Rica

EcuadorEcuadorChileChile

VenezuelaVenezuela

ColombiaColombia

BrazilBrazil

Married Female Labor Force Participation:Latin America and U.S. (age 18 to 65)

Compare Latin Compare Latin America to U.S. America to U.S.

40 years ago40 years ago

Married Female Labor Force Participation:Mexican-born Women, 1970-2000

0

10

20

30

40

50

60

70

1970 1975 1980 1985 1990 1995 2000

Pe

rce

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in L

ab

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Fo

rce

Mexican-born Women Mexican-born Women in United Statesin United States

Women in Women in MexicoMexico

Working-Age Population in the Labor Force, by Sex

0

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40

50

60

70

80

90

100B

razi

l 19

60

Bra

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97

0B

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80

Bra

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99

1B

razi

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Ch

ile 1

96

0C

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19

70

Ch

ile 1

98

2C

hile

19

92

Ch

ile 2

00

2

Co

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bia

19

64

Co

lom

bia

19

73

Co

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bia

19

85

Co

lom

bia

19

93

Co

sta

Ric

a 1

96

3C

ost

a R

ica

19

73

Co

sta

Ric

a 1

98

4C

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20

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Ecu

ad

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19

62

Ecu

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19

74

Ecu

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19

82

Ecu

ad

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19

90

Ecu

ad

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20

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Me

xico

19

70

Me

xico

19

90

Me

xico

20

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Ve

ne

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la 1

97

1V

en

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19

81

Ve

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0

Ch

ina

19

82

Vie

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19

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Ke

nya

19

89

Ke

nya

19

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So

uth

Afr

ica

19

96

So

uth

Afr

ica

20

01

Fra

nce

19

62

Fra

nce

19

68

Fra

nce

19

75

Fra

nce

19

82

Fra

nce

19

90

Un

ited

Sta

tes

19

60

Un

ited

Sta

tes

19

70

Un

ited

Sta

tes

19

80

Un

ited

Sta

tes

19

90

Un

ited

Sta

tes

20

00

Pe

rce

nt

of

Wo

rkin

g-A

ge

Po

pu

lati

on

Males Females Persons age 16 to 65.

Persons with Completed Secondary Education:National Populations Versus Migrants to the United States

0

10

20

30

40

50

60

70

80

90

100

Brazil Chile Costa Rica Ecuador Mexico Vietnam Kenya South Africa

Pe

rce

nt

In home country, ca. 2000 Migrants to U.S. 1995-2000

Population Residing with an Elderly Person

0

5

10

15

20

25

30

1960

1970

1980

1991

2000

1973

1985

1993

1970

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2000

1989

1999

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1982

1989

1999

1962

1968

1975

1982

1990

1960

1970

1980

1990

2000

Per

cen

t o

f to

tal

po

pu

lati

on

Elderly persons (age 65+) Non-elderly residing with an elderly person

Brazil Mexico KenyaColombia VietnamChinaS Africa France United States

Percent deviation in intergenerational coresidence of each occupational group from nonfarm average: Younger generation

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

1850 1860 1870 1880 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Low status Mid status High status

core

side

less

tha

n av

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e

co

resi

de m

ore

than

ave

rage

Percent Female; Scientists and Engineers

0

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35

40

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2005

Year

Per

cen

t F

emal

e

Engineers

Scientists

IPUMS Graph from “A Century of Women in Science and Engineering,” History Day project by Abby Norling- Ruggles, age 12