1. Updating inclusion probabilities for the sampling units
13th Workshop on Labour Force Survey Methodology
Reykjavik, May 2018

3. Contents Sample Design: Main Features Types of updates
Quarterly updates in the selection frameworks.
Updating probabilities of the PSUs in intercensal periods.
General update process, making use of the information gathered from each census.

4. Sample Design: Main Features

5. Sample Design: Main Features
Sample design: stratified two-stage design
Frameworks
Area Frame : about Census Sections(geographical areas with inhabitants)
Address Register: list of addresses that was obtained from the most recent Spanish Census (2011)
Strata.- PSU’s stratification process is performed according to the size of the municipality which the census section belongs to. A maximum of 9 strata are defined in each province (NUTS3).
Sample size and allocation
Census Sections
Family dwellings
PSUs = 3822
SSUs= ( 21 per PSU)
About persons each quarter

6. Sample Design: Main Features
Selection strategy:
1st Stage: Probabilty proportional to size( number of households)
2nd Stage: Systematic sampling with random start and equal probability
Sample Rotation.- A sixth part of the sample of households is renewed each quarter. To this end the sample of PSU’s is divided into six subsamples named rotation groups.
Self-weighted sample Q1
Q 2
Q 3
Q 4
2015
2016
RG 5
RG 4
RG 3
RG 2
RG 1
RG 6
Recogida

7. Types of updates

8. Quarterly updates in the selection frameworks
When?
2017
2018
RG 5
RG 4
RG 3
RG 2
RG 1
RG 6
Data collect
Updating
Q 1
Q 2
Q 3
Q 4
Q 1
Q 2
Q 3
Quarter
How?

9. Quarterly updates in the selection frameworks
PSUs Frame :Introduce de reviews in the geographical bounds
SSUs Frame :register new dwellings, visit those which are empty or being used as secondary or seasonal dwellings and have become main dwellings

10. Updating probabilities of the PSUs in intercensal periods
When?
Every three years, we implement an updating probabilities process within fixed strata
How?
Two possibilities :
Selecting a new sample from the updated frame
A procedure that allows to update the probabilities of selection, making few changes of primary sampling units

11. Updating probabilities of the PSUs in intercensal periods

12. Updating probabilities of the PSUs in intercensal periods
Example Spanish LFS:
Last updating process of this type was carried out with a reference date of January 2017
143 PSUs are replaced from the total of 3,822 (less than 4%)
Incorporated into the sample as of the first quarter of 2018, per rotation group

13. General update process(Census information)
When?
Every ten years, using latest Census Information
This update affects many stages of the LFS Sample design:
Frameworks :
New ones will be used, replacing the previous ones
The are incorporated into the sample per rotation group

14. General update process(Census information)
2. Stratification and sample allocation
Register of the municipalities with their respective populations
Once the municipalities are assigned to their real strata, the PSUs are immediately assigned to their new strata
The allocation of the first stage sample among the strata is done proportionally to their population size

15. General update process(Census information)
3.Subtratification
Ward’s Method :multivariate cluster analysis algorithm
Two types of information are used at the PSUs level
Information from the last Census
% foreigners
% unemployed
% people between 0 and 14 years old …
Information from the Spanish Tax Agency

18. General update process(Census information)
4. Updating probabilities of PSUs
Brick Method
Similar Kish method, but with strata change
There may be discrepancies between the allocation obtained and that which is defined
The last time this methodology was used (2014)
478 PSUs were changed out of a total of 3822
The changes are incorporated into the sample per rotation group,in 12 quarters