I am interested in understanding whether a proportion of a subgroup of people is increasing over time in various teams. There are two scenarios for why the proportion could increase. One, more people from that subgroup join the team. Two, some people from the other subgroup leave the team. How can I account for these processes in the model? In other words, how do I make sure that if I see an increase in the proportion of interest, it is not because of teams generally getting smaller?
The options I have considered so far: 1. Exclude the cases that fit scenario two. Because this scenario is not of interest and does not mean a real increase in the proportion. 2. Include team size as a covariate. Problem here is that if team size decreases because of the person of the key subgroup leaving, that is an important event.
Is there some really straightforward answer here that I am missing?
Thank You