Possibly not what's happening, but this is a well-known occurrence in comparing subsets to an overall set. It's called Simpson's Paradox: https://en.wikipedia.

Possibly not what's happening, but this is a well-known occurrence in comparing subsets to an overall set. It's called Simpson's Paradox: https://en.wikipedia.org/wiki/Simpson%27s_paradox https://en.wikipedia.org/wiki/Simpson%27s_paradox