does anyone have numbers for how many are dropped?

well lets put it this way: max number of girls in a pc can be around 75 people
11 chapters
lets say every chapter gets 75 girls (some will get less, but I'd say 75 max)
then a generous number of people in chapters for 2020 would be 825 girls
about 1200 went through last year, and if the same go through this year then roughly 375 or more will either be cut or drop. The numbers of pledge classes vary because a lot choose to drop and get cut. But i'd say over 400 got cut or dropped out last year

also if you maximize your options (your recruitment counselor will go into more detail) then you are guaranteed a bid! girls who end up not having a house either drop themselves or don't maximize their options so it cuts them out of the system. again, your RC will go into more detail

so I don’t know the exact stats from last year but I know the year before 96% of the people who went through recruitment joined. another thing to note is that some of the people who dropped out of formal recruitment later joined through informal.