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human
Why do economists not look at income data at the individual level?

Edit: Please ignore my claim that the UK provides long term income data at the percentile level- I misspoke (aka was stupid and wrong) and the closest I can find to this now is annual income by decile. Apologies for any issues/trouble.

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I am a political science grad and one of the things that has been bugging me for the years now is why it is so hard to find long-term data on income over time for individuals. I live in the UK, and it is possible to view income over time by percentile (and therefore see, for example how the income level of the 10th percentile has changed year on year), but I have been completely unable to find any source of data detailing the yearly or quarterly changes of income for individuals over any extended period of time.

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This was not core to my degree, or the work I do now, but I have a genuine curiosity about a) what the financial history of individuals in this country (and many others) look like (how many trend up, how many trend down, to what extent, and in what distribution etc) and b) whether there is any connection between, for example, upwards or downwards trending personal financial history and political orientation, levels of political engagement, etc. I feel like it would be a useful way of collecting and consolidating data, but it also does not seem to be done, so I just wondered why that was. I understand that privacy would be a major concern, and that ethical considerations of data use would be important, but if these concerns can be addressed, would this not be something economists would find useful? PoliSci nerds definitely would.

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P.S. If the issue is a logistical one, why is that the case? I understand that it might be tricky to survey large numbers of people independently, and unlikely that all of them would even reliably report back yearly income from far in the past, but wouldn't tax returns serve as a valuable source of info?
gpt
Data tracking individuals over time is called "panel data," and there are some studies that analyze it. Try searching for "panel data" and whatever your topic of interest is. For the US, the National Longitudinal Study of Youth has high-quality panel data covering a wide range of topics.

I think I've heard of researchers getting restricted access to anonymized tax data, but the publicly available data is all aggregated, for privacy reasons. Even anonymized data might have enough information to identify specific individuals.