Understanding Society User Support

We saw the Understanding Society Design Overview and would like to seek your expertise on some of the queries that we have:

1) Are respondents required to answer questions related to household income in the survey?

2) Does the study track household income across time? If yes, could you share more on the data processing methodology? E.g. How does the study treat the problem of household formation/dissolution? If household A splits into household B and C in year X+1, does the household income figure follows from household A to B or household A toC?

3) We note that it is mentioned that the study is representative of the whole population across time (as a result of births to sample members joining the sample). Would the study be representative of the population if over the years the country has more and more new immigrants? (Note: these new immigrants would not be part of the OSM in wave 1 and will not be related to the original households. As such, they will never be part of the survey sample.)