Understanding Society User Support

Thanks Stephanie.

So, to put it differently, whereas in BHPS waves pretty much align with years (e.g. in a panel data study one could replace wave with year), this is no longer the case in US, as waves actually run for two years. So, to assign years from US into a panel data analysis one requires to use information from "istrtdaty" and "istrtdatm" variables in order to assign interviews to BHPS-type waves. In this sense, there is a sampling "dip" in the panel-data structure for those individuals coming from BHPS into US in 2009, because BHPS interview dates were mainly in Sept-April, whereas BHPS "2009 cohort" was interviewed in Jan-Dic 2010, and thus, some of them would belong to the "2010 cohort" in BHPS.

This clarifies my issue. However, as far as a I can see, there is no mention of this in the documentation. And yet, this is crucial for anyone using panel data analysis. For instance, if one wants to add a time trend, or use year-dummies, using waves as years is misleading, because within waves the response of an individual (e.g. wages) refer to June of year X whereas for another individual in the same wave it corresponds to June of year X+1. This also means that longitudinal weights are not particularly helpful either. Actually, given the new US structure, they are probably never helpful. The only solution is to compute them not based on the variable "wave" but on a manually derived "year" variable, which currently is not available. This is probably something to be considered for future releases, as the key purpose of US - panel-data analysis - is in my opinion severely hampered with the current interview/wave structure.

Best,
Luis.

Dear Luis,

This is not a sampling dip as the sample is not drawn each year, it is just a longer time between interviews than between other waves. BHPS Wave 18 interviews took place between September and December 2008 so it would be too soon to interview the same participants again starting in January 2009. Figure 1 of the BHPS-Harmonised User Guide clearly shows that they were not interviewed in 2009.

This working paper describes the sample design of Understanding Society and how the BHPS continuing sample members were incorporated into year 1 of Wave 2: https://www.understandingsociety.ac.uk/research/publications/514007

There is a guide to selecting weights in the User Guide, in section 3.9.1, including specific weights for using the BHPS sample members. If you have further questions on which weight to use I can refer this issue to the weighting team.

Best wishes,
Stephanie Auty - Understanding Society User Support Officer

Thank you Stephanie, that guide is very helpful. For the moment I've resolved the issue, so do not need further help with weights.

Best,
Luis.