Register-based census: Pros and Cons Anne HERM & Michel POULAIN November 2012

QUESTIONS ADDRESSED Development of census as a statistical data collection method on population in Europe What are the advantages and limitations of register-based census?

An inevitable move to the register based censuses in Europe In many European countries, the move to register-based census is a reality : Full register-based census was introduced first in Denmark in 1981. For the 2010 round census, 10 countries used fully register-based methodology for their census : Finland, Denmark, Sweden, Norway, Austria, Netherlands, Belgium, Switzerland, Slovenia and Iceland. In Belgium, Iceland and the Netherlands some surveys were also used in addition to register data. In 8 other country administrative register served as support for enumeration and as a source for basic demographic characteristics : Czech Republic, Estonia, Germany, Italy, Latvia, Lituania, Poland and Spain.

Why countries are looking for alternatives to the traditional population census? High cost of fieldwork that cannot be distributed over time Increasing negative public opinion linked to privacy Increasing problem of under-coverage (mobility of people) Low reliability of certain characteristics (e.g. linked to memory or refusal to give information ) Existing administrative registers as potential data source for substitute to traditional census Wish to avoid the additional cost of data collection that is largely done already in the course of administrative procedures

Two different ways to collect data Census: 1) statistical activity and product from the beginning to the end 2) one-shot data collection during a short fixed period 3) includes retrospectively collected data 4) presents the current statuses/characteristics of person Register: 1) product of administrative activity, to be turned to statistical product 2) collected continuously, at the time of event registration 3) presents the latest registered statuses/characteristics of person

What are Pros and what Cons CENSUS POPULATION REGISTER Statistical purpose as priority Specially for statistics Statistical data collection is not a priority Organisation of data collection One-shot data collection Continuous data collection Coverage More or less exhaustive coverage of present and possibly usually resident population. Depends on availability (+willingness) of persons for enumeration. May include illegally resident persons or non-registered statuses Exhaustive coverage of legally resident population, more or less exhaustive coverage of (permanent) resident population. Depends on legislation, admin rules as well as interest/incentives of person (and of administration) to register/deregister. Excludes undocumented persons/events.

More about Pros and Cons CENSUS REGISTER Methodology improvement Ad hoc methodology with concepts and definitions for census, possibilities to adjust according to the current (but decennial) needs Definitions and availability of variables depend on legislation that define the contents of the register, relatively difficult to adjust Amount of data collected Main demographic characteristics and selection of socio-economic variables. Limited to the length of the questionnaire that has impact to cost of data collection Main demographic characteristics are available. Number of socio-economic variables are limited Consistency between population stocks and flows No consistency a priori Consistency with all registered events (birth, deaths, marital status changes, migration events, citizenship acquisitions etc)

More about Pros and Cons CENSUS REGISTER Cost of data collection Usually expensive, must cover cost of all elements of data collection (methodology, fieldwork organisation, processing raw data etc) No additional cost or limited cost for data collection, some cost for methodological support, limited cost for raw data processing Cost of statistical data processing Low relative to the cost of data collection High relative to the cost of data collection

Some methodological problems linked to registers How close is legal population to usual population Difficulties to apply definition of household (housekeeping concept not applicable; household-dwelling concept needs good dwelling register) Difficulties to apply definition of family nucleus in case of partners in consensual unions Difficulties to find data on topics where events are not registered continuously or they are registered in various separated registers (activity status, job) No information or there are gaps on events that were not registered in country (received education and change of marital status abroad) No data on events that happened before the registration started (year of immigration) Impossible to introduce new topics (on which data are not in registers)

Advantages of using registers In long term perspective the cost will be low More frequent ‘censuses’ and annual data consistent with ‘census’ data Possible to construct longitudinal data on all registered events, while collection of data was at the time of event. Possibility to link stock data (status at fixed time) with flows data (change of statuses). Possibility to enlarge the amount of data by linking data from various registers (no limit on number of topics in questionnaire). Possibility to find data on persons/households who left country before census date.

Quality and completeness of data from registers Depends on strength of administrative system and legislation/rules for registration, readiness of people to follow these rules, the successful collaboration between statistical and administrative bodies (analysis as a tool for improving data quality), method used for collecting basic data in the register and time during which the register is improved.

Long and careful preparation Step by step by introducing registers for statistical use, starting from population register adding others. At least 4 basic registers: PR, dwellings register, enterprise/legal entities register, education register Unique personal identity information is needed. Every register are tested separately and used for statistics before census. For pioneer countries in register-based censuses it took several decades from partly to fully register-based census. And still problems to solve.

A methodology project in Estonia In Estonia , the work for 2020 census started in 2010, involving demographers, sociologist and geographers as well as experts in other fields. Inventory of all existing adm registers, including related legislation, the rules for maintaining registers, data included, population covered, links with other adm registers. Working out the algoritm (rule) for constructing every census variable. Tests of quality of currently existing data in registers, including consistency , completeness, coding etc and comparing with other registers. Identifying the needs for improvement, of contents, legislation etc and formulating relevant proposals.

Let’s be ready to use the new possibilities offered by register-based censuses ! Thank you! Acknowledgments: This research was supported by the Estonian Ministry of Education, Science research theme SF0130018s11 and ETF grant No 8904 .