I know those gaps are often due to the data coming from different sources and it's not always possible to normalize it and what not, but I'm always super suspic

I know those gaps are often due to the data coming from different sources and it's not always possible to normalize it and what not, but I'm always super suspicious when they do that. Also when you see results that are like 1953-1986, like maybe the results from 1952 and 1987 invalidate whatever point they want to make, so they used only the section that helps their case.