What is the average approval of the past 4 US presidents, from George W Bush to Joe Biden so far? I want the approval weighted by how many days the approval poll was taken.
FiveThirtyEight has an ongoing project which tracks Joe Biden's approval rating and compares it to each president since Truman on a day-by-day basis. I think that would probably provide the closest answer to what you're looking for; to get an "average" for a President's full term would require a lot of choices to be made as far as what polls to include, how to weight different polls (not just by the length of data collection, but also by the number of respondents, the method of contact, the pollster's history, etc.) and would likely be a significantly-difficult project in its own right.