Updating inclusion probabilities for the sampling units 13th Workshop on Labour Force Survey Methodology Reykjavik, 17-18 May 2018

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.

Sample Design: Main Features

Sample Design: Main Features Sample design: stratified two-stage design Frameworks Area Frame : about 36.600 Census Sections(geographical areas with 500-2000 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= 76400 ( 21 per PSU) About 160.000 persons each quarter

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

Types of updates

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?

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

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

Updating probabilities of the PSUs in intercensal periods  

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

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

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

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

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