Symposium
2001/12 6
July 2001 English only
|
Symposium
on Global
Review of 2000 Round of
Population and Housing Censuses:
Mid-Decade Assessment
and Future Prospects
Statistics Division
Department of Economic and
Social Affairs
United Nations Secretariat
New York, 7-10 August 2001
Traditional
censuses versus alternatives: Ireland*
Aidan
Punch **
CONTENTS
B.
Have traditional censuses had their day?
C.
Administrative registers: a statistical panacea?
1.
There are many reasons for conducting censuses of population. At the
most fundamental level a census provides a population headcount at the national
level. Depending on how the census is organized, this national total may be
broken down by detailed geographic area. Indeed, the taking of a census may
even be enshrined in the constitution of a country for the purposes of
determining political representation. In addition, budgetary allocations
invariably hinge on census outcomes. However, notwithstanding the legal or
quasi-legal nature of the census objectives at the national level, the richness
of the data provided and the small-area dimension of the census are its
greatest assets. Against this backdrop, therefore, the decision as to the best
means of conducting the census is one which national statistical institutes do
not take lightly.
2.
At opposite ends of the methodological spectrum are traditional
censuses and those carried out using registers. In between are various
combinations of the two—that is, mixed
models, supplemented in some cases by sample surveys. Traditional censuses are
commonly taken to mean those in which members of the public are requested to
respond to a census questionnaire and where a field force of enumerators is
involved in the field operation either delivering blank forms or collecting
completed ones, or both. In its purest form a register-based census will,
through the use of various statistical techniques, combine results from
existing administrative registers at the micro-level to produce census-type
information.
3.
Which is the best method to use? What considerations should inform our
decisions? What price accurate statistics? These are some of the questions
addressed in the remainder of this brief note.
4.
Staging a traditional census is a multifaceted project involving some
or all of the following components:
·
Holding a census pilot to test new question wordings or amendments to
existing ones;
·
Getting government agreement to the final census questions;
·
Determining appropriate census geography to ensure manageable workloads
for enumerators;
·
Recruiting and training a field force to carry out the census;
·
Handling support activities, such as field force payments, warehousing,
transportation and logistics;
·
Conducting a public awareness campaign to highlight the importance of
the census and the need to comply with its provisions;
·
Using technology to ensure the speedy processing of the information
returned on the census forms; and
·
Making the results available as speedily as possible using up-to-date
methods which are responsive to users’ needs.
5.
Cost is normally cited as the main disadvantage of the traditional
census. Indeed this has now almost become part of the lore in some
international organizations with national statistical institutes being
admonished to move to the more enlightened (and cheaper) register-based
approach. If this assertion is repeated often enough, then traditional censuses
may just eventually be seen as a bad thing. However, while not wishing to
downplay the importance of cost, the investment made (and that is precisely
what expenditure on a census is) has to be viewed in the context of the likely
benefits which will flow from this investment. As it is not possible to
formulate policy in a vacuum, the provision of comprehensive and timely
information, such as that provided by the census, is a prerequisite for
informed decision-making. It is highly questionable whether a move to a less
preferred (and maybe less accurate) method of carrying out the census in order
to reduce expenditure is the most cost-effective solution in the longer term.
6.
So, precisely what are the advantages of traditional censuses? First is
the fact that the national statistical institute has control over the
operation, which means that it can be organized in a streamlined and uniform
manner conducive to optimizing its statistical potential. The comprehensive
nature of the census in terms of topic coverage should not lightly be
overlooked when compared with some of the alternative approaches. And there is
the positive spin-off which the census generates for official statistics in
general, through its public awareness campaign. As well as engendering a sense
of national participation it presents an opportunity to the national statistical
institutes through its spokespersons to highlight the importance of objective
and timely statistics for society at large.
7.
On the downside is the aforementioned cost argument, which cannot be
ignored, especially when public finances are under pressure. To illustrate that
cost is a real issue, there are many instances of censuses being cancelled
because of budgetary cutbacks. This happened in Ireland in the mid-1970s,
unfortunately (with the benefit of hindsight) at a time of major demographic change.
8.
A successful census field operation requires not only detailed and
painstaking planning but also a modicum of good luck. This was singularly
absent in the case of the planned 2001 census in Ireland, when because of the
precautions in place to prevent the spread of foot-and-mouth disease, it was
decided to postpone the census for a year. The revised census date is 28 April
2002.
9.
Respondent burden is also a real issue to be contended with. On the
basis of crude estimates, the opportunity cost of completing the Irish census
questionnaire may be as high as a quarter of the overall census budget.
However, this is part of the price to be paid for quality information for
policy formulation and assessment.
10.
The fact that censuses are carried out infrequently gives rise to major
organizational headaches. However, if they are carried out every five years, as
is the case in Ireland, then the institutional memory both in the statistical
office and in the field means that the learning curve is not quite as steep as
it otherwise would be if starting from scratch every ten years.
11.
Finally, traditional censuses are finding it hard to grapple with
certain subpopulations, such as the single young mobile population, people
living in ghettos or shantytowns and marginalized sections of the community.
While these groups pose major problems for census takers it is unlikely whether
any other method of enumerating them would be any more effective.
12.
The major positive factor associated with using administrative
registers for statistical purposes is the fact that the same information is not
collected more than once. Where recourse can be had to existing data holdings
then, depending on their quality and coverage, they can be collated in order to
make them amenable to statistical reporting. They can also be merged with other
data sources in order to optimize the output being produced. This reduces the
burden on the respondent by making use of whatever data are already in the
system. The immediate saving is financial. Costly field procedures are avoided
and most effort is concentrated on improving the quality of the registers
themselves and using relevant statistical techniques to derive the required
output.
13.
The national statistical institute has greater control as well over
timing issues. In theory data sets can be merged at any time allowing great
flexibility in terms of reference date and periodicity.
14.
However, there may be drawbacks to using administrative registers as a
source of statistical data. At the basic level is the degree of compliance with
the register on the part of the public. This has an impact on both the coverage
of the register and on the accuracy of the information contained in it. Where the
administrative rationale for registering correctly and on time is strong, then
the accuracy of the register is likely to be high. But is this always the case?
In societies which are highly regulated, the public may be used to and accept
the need to register for various public schemes. Even in these cases there may
be reasons why individuals would not want to register. A lot depends,
therefore, on the degree to which the administration maintains its register and
sorts out its shortcomings.
15.
A definite drawback is that the information provided may not be
precisely what is required for statistical purposes. In some cases no
information at all may be available on certain topics. However, it is a choice
for the national statistical institute to make: either to settle for what may
be a suboptimal source of data because of cost considerations or to mount a
statistical operation which will have direct financial and indirect response
burden implications.
16.
The public also has to be assured of the confidentiality of the
statistical process. In other words, they have to understand the distinction
that individual identifiable data on administrative registers may be used by
the national statistical institute for statistical purposes (indeed, merged
with other such data) but that no such information passes from the statistical
office to any outside agency (the so-called one-way street). Not only do they
have to understand such subtleties, but they also have to implicitly trust the
national statistical institute to do the right thing. Direct statistical
inquiries have the merit that the methods used can be easily understood by
members of the public. Complex data merging and register cleaning do not have
the same simplicity.
17.
Censuses are national instruments paid for out of taxpayers’ money. It
is for the countries themselves to determine what offers the best value for
money, taking account of such factors as direct financial cost, data quality,
burden on respondents, public acceptability and so forth. Indeed, in some
countries there may be no real choice, as the traditional census may have
fallen into disrepute for various historical reasons.
18.
Where the choice exists between mounting an expensive field operation
or using excellent data from registers, then this will be a simple matter.
However, life is rarely that simple. In countries where good administrative
data are limited it may not be feasible either politically or culturally to
rectify the situation in the short term. Neither is it sufficient to say that
registers should be put in place in order to reduce the cost of collection of
statistics. Experience shows that there has to be a very strong administrative
rationale for developing and maintaining register-based information. Without
that, the level of compliance by the public will render any information which
may flow from the register to be of limited use for statistical purposes.
19.
The real choice is not between one end of the spectrum and the other
(i.e., traditional versus register). In reality many national statistical
institutes use combinations of direct collection and administrative
information. For instance, use may be made of national address databases to
assist in the field operation. Ultimately, national statistical institutes are
accountable for the money they spend. They therefore have to justify to the
government that the census will be carried out in the most cost-effective way
possible. If the government sanctions this expenditure (even if it is the cost
of conducting a traditional census), it does so bearing in mind that it is an
investment in the knowledge necessary to be able to formulate public policies
which are well informed and of long-term benefit to citizens.