Jean-Michel D urr Ministry of Education, France

2° CONFEST - 21-25 de agosto de 2006 - Rio de Janeiro

Reengineering of the population census

the french experience and its lessons for

implementing new censuses

Jean-Michel DurrMinistry of Education, France

Former director of the project for redesign the french census – INSEE


The goals of a census

• Provide official population (enumeration) : state, regions, municipalities… :– to share public funds on the population basis– Seats at parliament

• Describe characteristics of population and dwellings :– Sex, age– Employment– Migrations– Place of work, commuters– Households– ….

– >>> at any geographical level

• Sample base for household surveys


The traditional census

• Main features :– Exhaustiveness– Simultaneity– Every ten years or about

• Advantages :– Coherence of the data : snapshot of the population and dwellings– Data for any geographical level available– Mobilisation of the population and the teams

• Drawbacks :– Sample for some variables– Refreshment only every 10 years– Problem of quality due to the importance of the operation and

the lack of capitalized experience– Fixed dates : may not fit to the evolution– Risk for boycott– Cost of te operation (inc. intercensal headcounts)


Freshness

• Refreshment only every 10 years : sufficient in the past, but no more :

• Increasing demand for more frequent local data :– changes in population are going faster :

• urbanization, • migration, • social behaviour...

– More and more utilisation at a local scale : decentralization, local area policies


Quality

• Huge operation, difficult to manage and to ensure quality• unsufficiently skilled enumerators• problem to capitalize experience• allways changes in methodology or definition• problem to compare censuses over time :

– the example of migration :

• Populationcensus N+10 - Populationcensus N is supposed to measure the evolution of population :

= Births + Deaths + balance of migration

• but affected by differences of quality ot the two censuses : if the balance of migration is 50 000 and census N overestimates population of 25 000 and census N+10 underestimates of 25 000, the balance of migration will be estimated to zero.


Fixed date

• The dates of the censuses may structure the analysis of the evolution and may hide the real process :

1980 1985 1990 1995 2000 2005

% people living in periurban areas


The situation in the world

• Mainly decennial census, – Registers in certain countries, but often problem of quality– Sometimes intercensal headcounts (very costly)

• Increasing demand : – Rapid changes in population and urbanization– At a local scale : decentralisation, more power to local authorities– Users ask for more frequently refreshed information

• Concerns about quality and efficiency of the operation

A need for finding new ways• A lot of projects or studies for new methods of census :

– Spain, Germany, Israel : register based census– Netherlands : virtual census based on surveys linked to the

register– France, USA, Peru : use of rolling census– Brazil : studies for redesign the census– UK, Mexico : studies (surveys + register)– ...


The situation in the world - ECE

Method 2000 2010

Traditional census 35 22

Based on registers 3 7

Registers + headcount 5 4

Registers + surveys 1 8

Headcount + rolling census - 1

Rolling census - 1

Total 44 43


New methods ?

• Get free of the dogmas of :– Exhaustiveness :

• Use sample

– Simultaneity :• Collect information at different time and combine it

• And many combinations are available :– Sample/exhaustive surveys– Register/administrative sources– Multi annual combination – …


The situation in the 90’s in France

• General censuses since 1801, every 5 years until 2nd world war

• Increasing periods between censuses : 7, 8, 9 years due to budget consideration

• Insufficient legal basis :• periodicity• Insee and the municipalities’ function

• Increasing demand for information : • At a local scale : décentralization, more responsibility for municipalities, regions• Fresher data

• No population register

• Progress in :– Sampling techniques (well-balanced)– Geographic information systems (GIS)

• >> Reconsider traditional general census using rolling census techniques


Rolling census

• Principles :– Ideas of Kish (1980, 1990…)– Combination of data collected at different

periods– Cumulative survey covering a whole country

over a period ot time rather than a particular day :

• Produces annual and multi-year estimates• Produces information for all areas • updated every year

– Exhaustive enumeration or sample


Another rolling census experience

• American Community survey :

– Implement a national sample of 3 million addresses

– Profiles every year for communities of 65,000 or more, beginning in 2004 and each year thereafter

– 3 to 5 year cumulations for communities of less than 65,000 population

– but insufficient sample to replace the decennial headcount


Methodology

• constraint :– Same budget as for a general census : every year, 1/7 th of the

general census budget

• 5 years cycle : – Produce 3 years old data

sampling : survey 5/7 (70%) of population over 5 years


Francenumbers almost36 000 communesunder 10 000inhabitants (almost30 millionsinhabitants).These communesHave been spreadinto 5 groups

WHEN ?

WHO ?

HOW ?

HOW MUCH ?

Each year, in january and february, to avoid problems of seasonal effect

One group enumerated each year,More than 7 000 communes

Survey on every inhabitant of the communes of the group.In 2004, every inhabitants in the communes of first group,In 2005, every inhabitants in the communes of second group,etc.

Over 5 years, every inhabitant of the communes under 10 000 inhabitants is enumerated

Communes under 10 000 inhab.


A year for every commune

In 2009,we go on …

(exemple of Bas-Rhin)

"communes 2008" (less than 10 000 inhabitants)




"communes 2004« (less than 10 000 inhabitants)

Communes concernées chaque année(10 000 inhabitants or more)

Haguenau

Strasbourg

Sélestat

Saverne


France numbersalmost 900communes over 10 000inhabitants :near30 millionsinhabitants

WHEN ?

WHO ?

HOW ?

HOW MUCH ?

Every commune every year

Survey on a 8 % of the dwellings sample each year

Over 5 years, 40 % of the population issurveyed

Communes over 10 000 inhab.

Each year, in january and february,to avoid problems of seasonal effect


A group of buildings sampled every year

In 2009,we go on …


Estratos equilibrados< 10.000 habitantes (36.000 comunas/30 milhões hab.) 10.000 habitantes (900 comunas/30 milhões hab.)

•Comunas < 10.000 hab.– Seleção de 20% das comunas por ano– Enumeração exaustiva nas comunas selecionadas – Todos os endereços visitados em 5 anos

•Comunas >= 10.000 hab.– Todas as comunas visitadas anualmente– Visita a 8% dos endereços de cada comuna/ano– Serão visitados 40% dos endereços em 5 anos

Estratos adicionais : domicílios coletivos (internatos, instituições etc) - 20% visitados a cada ano

Plano amostral : resumo


The new census will produce every year :

• De jure population for every commune and administrative district : enables to take more frequently in account changes in population– > more equity

• Detailed statistical results :– At every geographical level

(micro data file for tabulation) – Combining data collected during the 5 last years– Relevant for the medium year (Y-2)

• Overall estimations at national and regional level : based on data collected the last year


Cumulating information

2004 2005 2006 2007 2008 2009 2010 2011

1

2

3

4

Group 1 Group 2 Group 3 Group 4 Group 5 Group 1* Group 2* Group 3*

* Including updates

Year of collection

5


How to estimate population of communes < 10 000 inhab. in Y-2 ?

Y-5 Y-4 Y-3 Y-2 Y-1 Y

I

II

III

IV

V

2AIIIR

5AVR

4AIR

3AIIR

1AIVR

AVR

2~ AIR

2~ AIIR

2~ AIVR

2~ AVR


Communes > 10 000 inh.

• 8% sample every year

• Mobile sum of the data collected 5 latest years

• Weighted according to the Y-2 RIL (number of dwellings)


Why Y-2 ?

• Medium year of the set of data

• At most 2 years between observation and estimation

• Mobile average in large communes

• …

• But it is possible to estimate Y with the same set of data collected over Y-4 <-> Y


Agenda

• 1995 : first report

• 1998 : beginning of the project

• 2004 : beginning of the new census

• 2005 : 1st overall estimations (France-regions) : some criteria

• 2006-2007 : Overall estimations (France- regions) : all criteria

• End of 2008 : first de jure populations

• 2009 : « cruising speed » dissemination


Utilisation of the new rolling census data

• General census : a snapshot every 10 years

• New census : not a movie, rather a slideshow– communes < 10 000 inhab. : more frequent full enumeration – communes > 10 000 inhab. : sample survey, but annual

update :• Suburban districts evolution : for example, changes in the social

characteristics• local decisions• no more dependent on the date of the census

• Any level : annual update


Rolling samples : two approaches

– Things are not changing too much during the period : as if you take a picture with a long exposure time. A certain fuzziness is acceptable

• If the period is long, for example 5 years, you may consider you estimate the middle year to consider a shorter period (2 years) between observation and estimation

– Things may change over the period : • you may collect relevant information for each period and

combination gives a stronger estimate for an average mobile mean.

• Otherwise, possible use of small area method (with complementary sources or not)


Flow data : example of migration

• For example, estimate migration over 5 years :– At country, state, region level, the annual sample is

relevant enough : • compare population between the present year and 5 years

before to calculate the balance of migration. Less problems of quality differences to compare

• use the question « Where did you live 5 years ago » to build the matrix of flows (region x region)

– For small communes, enumerated every 5 years : • compare population of the year to population 5 years ago

to calculate the balance of migration• matrix of flows over 5 years :

– the former place of residence of immigrants has been collected at the last survey

– the new place of residence for internal emigrants has been collected over the last 5 years in the other communes


Example : commuters

Urban area of Montpellier :

- 380 000 inhab.

- 45 000 surveyed every year


How to take benefit of that experience for implementing new censuses

Not a unique model :• When get free of the two dogmas of exhaustivity and

simultaneity, a lot of frameworks are possible :– Sample/not (e.g. : spread the whole population over 10 years)– Level of sampling : commune, building, dwelling…– Use of administrative data/not– Data collection over year/one moment in the year

• Example : french and american experiences are very different but based on the same principles

• So : necessary to find the best way according to the national context


Thank you for attention

Any questions ?

Jean-Michel D urr Ministry of Education, France

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