The new HBS

1
The new HBS

• Chisinau, 26 October 2007

2
Outline

• How the HBS changed
• Assessment of data quality
• Data comparability
• Conclusions

3
Key improvements in the HBS

• In 2006 the HBS was changed with respect to two
  major areas characterising a survey
• Sampling the way in which the sample is selected
  was changed in the following aspects
• Sampling frame
• Sampling design
• Practice of substitution
• Questionnaires these were changed to better
  monitor poverty and living standards
• We first look in detail at changes in sampling
  and then we explain those related to the
  questionnaire

4
An old sampling frame

• A sampling frame is the basic structure of
  information that is used to draw a sample
  population of different villages, cities and
  lists of households
• The HBS has been conducted from 1997 to 2005 in
  the same enumeration areas (villages and city
  districts)
• Such enumeration areas were considered to be
  representative and were selected based on
  population information gathered through the 1996
  electoral lists (the sampling frame)
• At that time the electoral lists were the best
  information available, better than the 1989
  Census
• Because of population changes and migration,
  information in the electoral lists was becoming
  increasingly biased, in some villages the list of
  households was exhausted
• In 2005 the NBS obtained updated and more
  comprehensive information through the 2004 Census
  as well as a database of electricity consumers
• Therefore, from 2006 both Census and the
  electricity database has been used to select the
  HBS sample

5
Sampling design

• The sampling design defines the main
  characteristics of the sample number of
  enumeration areas, total number of households,
  country regions for which estimates are reliable
• Although the sample size in 2006 is the same as
  in 2005, the number of enumeration areas
  increased from 45 to 120, thus ensuring a better
  coverage of the country
• Until 2005 the sample was designed to be
  representative for three different regions
  cities, towns and rural areas
• Now the sample is representative not only of
  these three regions, but also of four economic
  zones (North , Centre, Chisinau and South)
• Chisinau and Balti are now better covered and
  stratified for low and high income areas

6
HBS coverage of Moldova

• 2005 2006

7
The practice of substitution

• Until 2005 if a household did not want to be
  interviewed it was substituted with another
  household
• This created a selection problem households with
  children tend to refuse interviews more than old
  people
• From the enumerator perspective some households
  are easier to interview and the practice of
  substitution can create some distortions, the
  enumerator may not put all the efforts in trying
  to interview the originally selected households
• The consequence is that the sample becomes less
  representative proportionally more elderly
  people than in the actual population are
  interviewed and this in turn affects some of the
  key estimates (consumption, income, etc.)
• From 2006 substitution is no longer allowed and
  enumerators are encouraged to interview only the
  initially selected households

8
Questionnaire improvements

• In 2004 and 2005 the NBS conducted various
  experiments in order to improve the questionnaire
  design, such experiments guided the changes
  implemented in 2006
• Questionnaire changes affected the following
  areas
• Changes in the reference period of some income
  sources and expenditure items
• Improved layout of the diary (the questionnaire
  booklet that helps the household to record income
  and expenditure transactions)
• Food expenditure recorded only for half a month
  not the full month
• Changes in the definitions of employment
  indicators

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Effects of questionnaire changes

• Collected information can now be used to produce
  both accurate averages for the National Accounts,
  weights for the consumer price index, and
  distributional data for poverty analysis. In
  particular poverty and inequality data have
  improved
• There is a reduced household burden for the
  participation to the survey (the household needs
  to spend less time to complete the required
  information)
• Improvement in the measurement of some key
  statistics (remittances and agricultural income)
• Employment data are now collected ensuring
  comparability with definitions used in the Labour
  Force Survey

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Outline

• How the HBS changed
• Assessment of data quality
• Data comparability
• Conclusions

11
2006 data quality

• Data quality can be assessed looking at internal
  data consistency, but also through external
  validation
• Internal consistency
• Relationship between aggregates, prices capturing
  inflation, etc.
• External validation
• Some HBS estimates can be compared to those
  provided by other sources
• Such comparisons need to take into account
  differences in ways measures are obtained

12
Data validation with external sources

• Demographic indicators Census
• Composition by age
• Household size
• National income and product accounts
• Social protection
• Labour Force Survey
• Agricultural statistics
• Lets see some examples

13
Age distribution HBS, Census and demographic
statistics
14
Household size

• Average household size, including people working
  abroad, is the same in the 2006 HBS and in the
  Census, but in previous HBS was considerably
  lower
• In 2006 distribution of household size is much
  closer to that of the Census

15
Outline

• How the HBS changed
• Assessment of data quality
• Data comparability
• Conclusions

16
Comparability issues

• The changes described earlier (sampling,
  questionnaires) affect the comparability of 2006
  estimates with previous surveys
• It is not possible to compare 2006 with previous
  estimates
• Lets make a simple example Assume that you are
  looking at a room from one specific corner
• This room between 1997 and 2007 has changed
  considerably
• The perspective that was good in 1997 is no
  longer representative now, some parts of the room
  are no visible
• In 2006 the perspective has changed and all the
  room became visible again

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No comparability

• Although the room is the same, we cannot compare
  2005 and 2006 estimates because 2006 data allows
  us to see part of the room that were not visible
  in 2005
• This means that if estimates in 2006 are higher
  or lower than those in 2005, we cannot conclude
  that estimates have increased or decreased
• For example, if the average household size in
  2005 was 2.5 and in 2006 is 3. This does not mean
  that households are now larger than before. The
  part of the room that we did not see before has
  clearly an influence on the new estimate

18
Demographic indicators

• Household size and type of households

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Example House types in cities

• Detached houses in 2006 are included in the
  sample frame they represent 16 of dwellings.
• In 2005 they appeared to be un-existent (due to
  the old sample frame)

20
Example income and consumption

• Both income and consumption are now estimated at
  much higher levels than in 2005
• This is in line with estimates from the National
  accounts

21
Conclusion

• HBS quality improved substantially and now
  provides data that are more representative of
  Moldova
• Higher data quality means
• Better understanding of poverty and its
  characteristics
• Greater ability to inform policy making and
  monitor policy impact in the future
• However, 2006 data are not fully comparable with
  previous estimates. The degree of incomparability
  was somewhat unexpected, but we need to consider
  that there was no point in keeping the old design
  if no longer fully representative
• To make sure that data remains representative,
  villages and enumeration areas will be changed
  over time and the sampling frame will also be
  updated using the electricity database and making
  a household listing of the new selected
  enumeration areas