Understanding Society User Support

Giulia,
Looks like it would be useful to have a short guide to the health condition module. This might take a little bit of time. In the short term, you would have to study the questionnaires to see how we ask this of new vs existing respondents.
The course materials here can give you some ideas of how to take the complex survey design into account in your estimates: https://www.iser.essex.ac.uk/bhps/courses

...,over(varname)

I guess Stata would protest if you ask for the mean of a variable over the same variable?
The data sets come with several weights each for a very specific purpose. The user guide is the best starting point to find out more about the different weights.
Hope some of these leads can be useful at least in the short term.
Jakob

Giulia,

With regard to your question on subpopulation use in estimation of standard errors, I feel this is a question for a theoretical statistician. Within Understanding Society dataset we suggest using subpopulation option mainly because it helps with good correction for clustering (psu's).

Yet, here is a discussion why subpopulation option is better for other esimtation:
http://www.ats.ucla.edu/stat/stata/faq/svy_stata_subpop.htm

The difference arises because with 'if' option standard errors are calculated using only the subset of the dataset. With subpop option stata uses the whole dataset for calculating standard errors. The article suggest that the latter is a correct way of calculating standard errors.

Hope this helps,
Olena