Hello Jakub,
It will depend on the type of analysis you’re conducting. Some variables and information are only available in the Main Survey, so you may need to merge datasets if you want to include them in your analysis.
For example, if you are analyzing pre-COVID-19 data, you would need to combine information from before April 2020, which means using Waves 10 and 11. However, this will ultimately depend on the specific nature of your analysis.
A useful resource for this is Section 10.7 of the COVID-19 User Guide, which provides guidance on working with these datasets. You can find it here: https://www.understandingsociety.ac.uk/wp-content/uploads/documentation/user-guides/8644_covid_19_user_guide.pdf
Additionally, you might want to consider using calendar year data, as this dataset has already been processed into calendar years. Currently, data for 2020, 2021, and 2022 is available. You can access it here: https://www.understandingsociety.ac.uk/documentation/data-releases/
I hope this information is helpful.
Best wishes,
Roberto Cavazos
Understanding Society User Support Team