A. Introduction
1.
In the Netherlands, a combination of administrative
registers and household sample surveys is the alternative for a conventional
census. In some other countries the census is entirely register-based. In this
short statement the use of administrative registers in replacing a census is
discussed. Some general remarks are made and the situation in the Netherlands
is described. The conditions are given under which the approach is feasible.
2.
There are a number of advantages of using
administrative registers for producing statistics in general.
·
Costs.
Usually, a register is constructed and maintained for administrative purposes
by a non-statistical institute and contains some information about a large
population. If the information in the register is useful from a statistical
point of view, it is very cost-effective to use such an information source,
especially if it can be obtained for free by the national statistical
institute.
·
Level
of detail. Usually, an administrative register contains a
limited number of characteristics for a large number of units. This in contrast
to a sample survey, which usually results in a large number of characteristics
for a relatively small number of units. A second advantage of using
administrative registers over sample surveys alone is that much more detailed
statistics can be obtained, at least for a number of variables.
·
Quality. The
information in a register may be more correct than answers given to a
questionnaire, both from a sample survey and from a census. A notorious example
is the variable “income”, which is more likely to be measured correctly in tax
files than by interviewing. Experience shows that also relatively
straightforward concepts like “number of rooms in the house” are not always
measured correctly in a survey: a respondent may give different answers, for
unknown reasons, in different questionnaires. On the other hand, the impression
in the Netherlands is that the quality of information, especially in the
population register, is good. It is extremely difficult to function in Dutch
society without being included in the population administration, and the data
in the register are important for a large number of aspects of daily life in
our country.
3.
The advantages listed are the reasons that many
national statistical institutes are interested in using administrative
registers in their statistical process. There are a number of complications,
however.
·
Permission
to obtain and use administrative registers. For continuity
reasons, it is important that the national statistical institute is guaranteed
access to a register over a long period of time. A statistical law in which
this is settled is very helpful. In the Netherlands there is such a law.
·
Undercoverage. A
register may contain only a selective part of the population of interest. For
example, the population register may miss a number of aliens. Another example
is provided by the employee insurance scheme registration system in the
Netherlands, which misses some “small jobs” like delivering newspapers.
·
Different
statistical units. The units in the administrative register may
differ from the required statistical units. For example, a benefits register may
give information about families, while information about households may be
required.
·
Different
concepts. The concepts measured in an administrative register
may differ from the required statistical concepts. For example, in the
Netherlands we tried to use the information about “educational attainment” in
the employment exchange register. It turned out, however, that the variable is
defined in a different way than the statistical concept.
·
Quality. The
quality of an administrative register may be poor and, even more problematical,
may not be constant. In the Netherlands we experienced this with the employee
insurance scheme registration system. It is important for a national
statistical institute to be involved in changes in key registration systems, but
this influence is not easy to obtain.
·
Missing
variables. Some important variables may not be available in
administrative registers, for example “occupation”.
·
Matching.
Matching various sources may be problematic. In the Netherlands, for example, there
is no unique way to write addresses and this complicates the matching of our
valuation of real estate registration system and the dwellings register.
4.
If all traditional census variables can be obtained
from administrative registers that are of sufficient quality, one may decide
that a census is not necessary anymore. In that case, census tables can be
published much more frequently than once every decade, as is usually the case
with a traditional census.
5.
If some, but not all, relevant variables can be
obtained in this way, a country can decide to have a traditional census and ask
only the information that is missing (the available individual register
information can be preprinted on the census form in order to be checked). A
country can also decide not to have a census, but to complement the
administrative information by having sample surveys. The latter choice has been
made in the Netherlands
.
6.
In 1991 the Dutch Parliament officially cancelled
Statistics Netherlands’ obligation to carry out a population census. The last
traditional census was held in 1971. The main reasons for abolishing the census
were the estimated low compliance among the population and the availability of
equivalent data sources at substantially lower costs. Another important aspect
is that the census results were not used for administrative purposes like the
allocation of central government funds to municipalities.
7.
To meet the demands of the 2001 round of population and
housing censuses in the European Union, linked microdata are used from various
sources. Actually, the census programme is integrated in the new statistical
process that Statistics Netherlands is implementing at the moment.
8.
In this new statistical process interrelated
micro-databases are constructed for a number of object-types (persons, jobs,
benefits, dwellings, businesses, etc.). In each micro-database, data about the
object type are matched on the microlevel. A micro-database can best be seen as
a matrix with the objects as rows and the variables as columns. In order to
construct it, it is essential to have a “frame”, that is, a list with all the
objects and some basic properties. The frame of the micro-database for persons
is the population register; the frame of the micro-database for jobs is
constructed by combining information from the employee insurance schemes
registration system, the survey on employment and earnings and the income tax
register. Matched to these frames are microdata from various sources:
administrative registers, sample surveys and EDI. The micro-databases are
edited and partially imputed. Moreover, the input concepts underlying the data
of the sources are translated into the output concepts underlying the
statistical estimates we wish to publish.
9.
In the new statistical process the micro-databases are
the start of the estimation process. Based on the matched, edited and
harmonized microdata, statistical estimates are produced, which can be simple
counts from an administrative register.
10.
The new statistical process depends heavily on the use
of administrative registers. In implementing it we encounter all the
complications mentioned in the previous paragraph. This is described in much
more detail by van der Laan (2000).
11.
As stated before, the Dutch census programme is based
on a system of micro-databases. The main advantages of this approach, compared
to a traditional census, are
·
Relatively low costs and response burden;
·
Integration of the census programme with the regular
statistical programme; and
·
Census tables are available on a regular basis instead
of only once every decade.
Disadvantages
are
·
Dependence on the content and quality of
administrative registers;
·
Consistency problems in the estimation stage; and
·
Less detail in publications about variables that are
available only in sample surveys and not in a complete administrative register
(in the Netherlands “educational attainment” and “occupation” are the most
important cases)
.
(and survey-based) census
12.
It is important to understand the conditions that have
to be fulfilled in order for a country to rely on registers (and surveys)
instead of a census. We feel that the following conditions are essential:
·
There should be a good actual population register. If
there is no list with all persons living in a country with some basic
demographic information (sex, age, municipality), a traditional census seems
unavoidable.
·
There should be a good register about jobs in one form
or the other. Detailed regional information about employment seems essential to
have.
·
There should be a housing register in some form. At
least a list should be available of all dwellings.
·
The level of detail required for variables that are
observed only in the sample surveys should not be too great.
·
Only statistical use should be made of the results
(unless they can directly be obtained from an administrative register used). In
combining information from various sources a lot of methodological choices have
to be made with respect to matching, editing, harmonization, etc. We feel that
we can obtain good estimates in this way, but we know that the estimates are
not precisely correct. If money is distributed to municipalities on the basis
of the results, or if the number of seats in Parliament is based on it, it will
be hard to follow such an approach.
NOTE
The views expressed in this
paper are those of the author and do not necessarily reflect the policies of
Statistics Netherlands.
Van der Laan, Paul (2000). The 2001 Census in the
Netherlands: Integration of registers and surveys. Paper presented at the
conference on The Census of Population: 2000 or Beyond, Cathie Marsh Centre for
Census and Survey Research, Faculty of Economics and Social Studies, University
of Manchester, Manchester, UK, 22-23 June.
Kooiman, P., and A.H. Kroese (2001).
Restructuring statistical processes at Statistics Netherlands. Proceedings of the Meeting of the International
Statistical Institute, Seoul, Korea.
