This document has been prepared by the Singapore
Department of Statistics. It has been issued
1. The United Nations (UN) recommends that
a national census be taken at least every 10 years.
As the value of census data is increased if it
can be compared internationally, the UN further
adds "countries may wish to undertake a census
in years ending in years ending in '0' or as near
to those years as possible.
2. Singapore's first census was taken in April
1871 as part of the Straits Settlement Census.
Since then, regular censuses were undertaken at
ten-year intervals up to 1931. The Second World
War delayed the next censuses till 1947 and 1957.
Singapore's first population census after independence
was conducted in 1970 in line with United Nations'
recommendations to designate years ending in "0"
as census years. The next two censuses were conducted
in 1980 and 1990.
1970 AND 1980 CENSUS
3. The 1970 and 1980 Censuses followed a
traditional fieldwork approach. In the first
stage, houses were numbered to ensure complete
coverage. The second stage involved a large
number of field interviewers visiting the households
to collect the information with paper forms
and pens. The large volume of information collected
was then processed through a cycle of coding,
data entry, verification and table generation.
4. In the mid 1980s, the People Hub database
was set up with unique identification number (UIN)
for each Singapore citizen and resident.
5. The 1990 Census capitalized on the potential
of the UIN for record linking and made use of
the People Hub as the basis of conducting the
census. Information captured in People Hub was
merged with a few other administrative databases.
As far as possible, the census forms were pre-printed
with data from the databases for verification
6. Field interview was still the main method
of data collection. However, respondents were
allowed to self-enumerate (i.e. fill up the forms
themselves) and return the forms to the interviewers.
About one-third of the respondents chose self-enumeration.
7. As in previous censuses, the data collected
were processed through a cycle of coding, data
entry, verification and table generation. The
1990 Census exploited the then database technology
running on a Fujitsu mainframe for data processing.
Coding was done by batch mode and extensive data
verification rules were drawn up for batch mode
checks on census records. Table Producing Language
(TPL) was used to generate the census tabulations.
2000 - A REGISTER-BASED CENSUS
8. Since 1990 Census was the first time that
a database was used to conduct the Census, it
was deemed necessary to verify the information
with those collected from the field. The results
were encouraging. Following this, a Household
Registration Database (HRD) was set up. Information
in the HRD originated from the 1990 Census and
is updated regularly by administrative data from
9. In many countries, a population census is
conducted together with a housing census to find
out the characteristics of dwelling units. Since
1980, DOS maintains an up-to-date database on
dwellings. In 1996, this database has been upgraded
and renamed National Database on Dwellings (NDD).
The NDD and HRD together give a physical location
for every household in Singapore.
10. With the basic or core items on individuals
and houses being available from the HRD and NDD,
it would suffice to conduct a register-based census
in the year 2000. Additional data required for
in-depth studies will be collected from a large
sample of the population. Experience from the
past censuses and sample surveys indicates that
a 20% sample would provide sufficient details
for in-depth studies and meet the need of the
majority of users.
11. A traditional census enumerates all persons
within the territory or country at the designated
reference time known as the "census day". This
is known as the "de facto" census. The "de facto"
census has the advantage of easy implementation.
The exclusion of residents who were temporarily
overseas and the inclusion of foreign visitors
do not pose a major problem with limited international
travelling in the past.
12. A "de jure" census on the other hand, enumerates
all persons at their "usual place of residence"
at the designated reference time. This will theoretically
cover all residents who are temporarily out of
the country. "Temporary or transitory" visitors
and "non-locally domiciled persons" are excluded.
However, it may be difficult to define "usual
place of residence" as well as "temporary or transitory"
13. A strictly register-based approach to Census
2000 meant that the population count will in fact
be "de jure". All Singapore residents who are
overseas will be included in the total population
count as their records will be in the database.
Similarly, foreigners living in Singapore will
be included, as their records will be merged into
the database from administrative sources. "Temporary
or transitory "non-locally domiciled persons"
will be excluded from the total population count.
However, following past census practice, a special
count will still be conducted for these groups
TRI-MODAL DATA COLLECTION STRATEGY
14. For the 20% sample enumeration, Census
2000 will adopt a tri-modal data collection strategy
comprising Internet enumeration, Computer Assisted
Telephone Interviewing (CATI) and fieldwork (with
15. The option of Internet Enumeration will
be made available to all households selected for
the 20 per cent sample of the population.
16. Upon the launch of the publicity campaign,
all selected households will receive a notification
letter with a password. Using the password and
the UIN, respondents who wish to be enumerated
by Internet would be able to log-on to their household
record in the database via the Census website
17. Some basic data already in the pre-census
database will be displayed. The respondent would
then proceed to fill up the rest of the census
questionnaire on-line. Various user-friendly help
features and explanatory notes would be provided.
The system will also perform simple on-line checks,
and prompt the respondent to re-enter data that
are clearly wrong or inconsistent.
18. Respondents will be given the option to save
and exit from a partially completed questionnaire
and fill up the remaining questionnaire at a later
time. Security features will be built-in to prevent
unauthorised access, hacking or jamming of records
over the Internet.
19. CATI was first deployed in the 1995 mid-decade
General Household Survey (GHS) covering about
300,000 Singapore residents. In the survey, some
two-third of the households were successfully
interviewed by CATI. The Department intends to
build upon the success of the 1995 GHS, and exploit
CATI as the main mode of data collection in Census
20. The CATI system allows the interviewer to
perform multiple tasks of interviewing, data entry
and simple coding simultaneously. With most questions
in multiple-choice format, the interviewer needs
only to point and click on the right answer. The
interactive environment also allows for automatic
branching of questions. For e.g., should the respondent
be a full-time student, the system will skip questions
on economic activity and move on to ask questions
on transport mode to school. Answers are automatically
coded wherever possible and updated into the database.
21. Households that have not submitted their
returns by Internet will automatically be scheduled
and dialed up for CATI interview after a cut off
date. Households with unlisted or without telephone
numbers could still opt to be enumerated by CATI
by calling the Census Hotline.
22. Like the Internet enumeration system, various
help features and explanatory notes will aid CATI
operators. The CATI system will incorporate streamlined
questioning. It will also feature on-line checks,
and prompt the operator to re-enter data that
are clearly wrong or consistent.
23. Records will be scheduled for fieldwork
if it could not be contacted by CATI after a fixed
number of telephone attempts. These records will
be grouped by areas and passed to regional census
24. Fieldworkers will visit these remaining households
to conduct face-to-face interviews. Should they
fail to contact these households, they would leave
blank census forms with these households who could
fill and mail the form back to Census Office.
All forms coming back from the field will be imaged
and the data captured through OMR software. Data
entry will only be necessary for descriptive fields.
of the various modes
25. The cost to Census Office varies according
to the mode of response chosen by respondent.
Field enumeration cost the most, as it is the
most labour intensive. This is followed by the
mailing method, which requires census officers
to scan in the forms returned and perform corrective
data entry for descriptive items. The expected
high proportion of incomplete forms also meant
that census officers had to contact the household
to fill up the missing data items. CATI interviews
are cheaper as data entry is directly done during
the interview and no transport time or costs are
incurred. Internet self-enumeration is the most
cost efficient, given a properly designed system,
as the respondents perform data entry.
26. It is difficult to estimate the proportion
of households that will be enumerated by the various
methods. The Internet penetration level in 1996
was only 8.6% of total households1. Furthermore,
Internet enumeration requires respondents to take
the initiative and play a proactive role.
27. On the other hand, a higher proportion of
households would already have Internet access
in their workplace or school. The PC penetration
rate stood at 36%1
in 1996. With the trend of PC vendors combining
PC sales with modems and Internet access, it is
likely that Internet penetration will move up
towards PC penetration levels. The many national
initiatives taken by the Government to provide
Singapore with an island-wide state-of-the-art
information infrastructure will also increase
the number of households with Internet access
1 IT Household Survey Report 1996 by NCB
Furthermore, the Inland Revenue Authority of Singapore
(IRAS) has recently launched E-Filing as a means
by which tax payers could submit their income
tax declaration form via the Internet. The response
from tax payers have been encouraging. With the
trend of government agencies moving in the direction
of electronic transactions, it is likely that
the population would become increasingly receptive
to the idea of providing census information via
PROCESSING AND VERIFICATION
29. Once data have been collected and stored,
the coding of descriptive items, mainly occupation
and industry begins. At the same time, data verification
is necessary to rectify inconsistencies, duplicates
or errors in the records. The experiences of GHS
95 and Census 1990 showed this to be very time
consuming. Officers verifying the records often
have to re-contact respondents to sort out inconsistencies
in the records.
30. Census 2000 will exploit the increasing computing
power of the PC by having enhanced data verification
checks at the front end. The CATI and Internet
systems will have more extensive on-line checks
for inconsistency and prompt the interviewers
to correct any data entry errors on the spot.
By shifting more verification checks to the front
end, more errors could be corrected at the point
of data collection, where the opportunity to double
check with the respondent is available, rather
than at the backend where re-contact with the
respondent is costly.
31. To handle the coding of descriptive items,
the Department had tied up with Kent Ridge Digital
Labs (KRDL), a research institute, to develop
the Advanced Coding Environment (ACE). ACE comprises
two distinct areas, namely the auto-coder and
the coding wizard software. The auto-coder performs
a direct string match with a dictionary of codes.
All records with distinct and non-ambiguous job
titles would be automatically coded in this way.
32. Records that could not find a perfect match
in the auto-coding phase would be channeled to
computer-assisted coding. At this phase, the coding
wizard provides intelligent assistance to the
human coders in searching for the correct codes.
Besides performing sophisticated string match,
the coding wizard engine would take into account
related fields such as the highest qualification,
income and age group in determining what are the
most likely codes for industry and occupations.
The wizard then list out the most likely codes,
in descending order of likelihood. The coder need
only analyse the record and pick the correct code.
STORAGE AND ANALYSIS
33. Data warehousing concept will be used to
manage the vast quantity of data efficiently.
Database warehousing is a major driver in IT presently
and offers a data storage architecture for collating,
processing and managing data from different sources
into a single repository so that analysis can
34. In addition to basic statistical tabulations,
data mining tools will be used during the analysis
stage to maximize the usage of the vast amount
of data. With the rapid changes in IT technology,
it will be prudent to keep abreast of the latest
development in new tools and programs and to finalize
the strategies nearer the data processing stage.
35. The register-based approach
to Census 2000, together with the innovative use
of the various technologies meant that only one-sixth
of the total number of census workers deployed
at the height of the 1990 Census would be required
for Census 2000.
36. However, with multi data collection modes,
it is necessary to recruit census officers with
better educational profile and IT skills. Training
of census officers will be given to equip them
with the skills to handle the various computer
systems and software. In addition, census officers
have to be trained on concepts and definitions,
line of questioning, responses to respondents
queries and soliciting complete and reliable answers.
37. The register-based approach to Census 2000,
supplemented by a large-scale survey as described
in this paper, will mark a watershed in the history
of census taking in Singapore. For the first time
since 1871, information will no longer be Acanvassed@
from the entire population. This is in line with
the approach taken by Denmark, Finland, Norway,
Sweden and the Netherlands.
38. Outside of Europe, Singapore would be the
first country to embark on the register-based
approach. In deciding to move in this direction,
the Department of Statistics had studied three
key issues. First, the quality of administrative
data in Singapore is sufficiently high to produce
an accurate count of the population and its basic
characteristics. Secondly, the legal framework
and data confidentiality practices in Singapore
permit the sharing of various administrative information.
Finally, the cost savings in adopting this approach
are substantial. It is estimated that the cost
of conducting a register-based census, coupled
with a large-scale survey, is only 40 per cent
of the cost of a full scale census.
39. Of the 163 censuses taken in 1990 round,
only 23 countries used more than one method of
data collection. Of these, only 2 countries adopted
a combination of three data collection methods.
The tri-modal data collection strategy adopted
for the 20 per cent sample enumeration is therefore
a bold experiment in multi-mode data capture and
the application of cutting-edge technology. Department
of Statistics views the integration of the various
modes as a critical success factor for Census
2000. To ensure smooth workflow and seamless transfer
of data from one mode to another, a census management
system will be built to track and move records
from one phase to another.
40. The heavy investment in IT for Census 2000
is expected to bring significant returns in the
future. The integrated use of the various technologies
in Census 2000 will set the foundation for the
Department's IT Vision for the future. This vision
seeks to provide a holistic solution to the entire
workflow in data collection, processing and publication.
Through an integrated electronic system, data
could be collected, processed and tabulated seamlessly,
so that the average turnaround time in the delivery
of output to the users will be vastly reduced.
41. Beyond 2000, the Department of Statistics
will look into a system of continuous measurement
of the population by tapping on the records of
the HRD and the NDD. A system of regular small-scale
surveys will be put in place to collect information
not obtainable from administrative sources and
to monitor population and social trends of current
Emerging Issues Related
to the 2000 World Population and Housing Census
Programme, by Sam Suharto (UNSD, Technical Notes,
Use of Administrative
Records in Population Censuses and in other
Demographic and Social Statistics, by Sirageldin
H Suliman (UNSD, Technical Notes, Nov 95)
Handbook of Population
and Housing Censuses, United Nations
The Register-based system
of Demographic and Social Statistics in Denmark
B an overview, by Lars Thygesen (Statistics
Journal of the United Nations ECE 12 1995)
The use of Identification
Numbers to link Information from Various Sources
and Create Alternative Statistical Units and
Concepts, by Finn Spieker (Statistics Journal
of the United Nations ECE 12 1995)
Evaluation of the results
of the Register-based Population and Housing
Census 1990 in Finland, by Riitta Harala (Statistics
Journal of the United Nations ECE 12 1995)
Which Countries will Follow
the Scandinavian Lead in Taking a Register-Based
Census of Population?, by Philip Redfern (Journal
of Official Statistics, Vol 2, No 4, 1986)