u/The_REDDITOR1324

Why is the arbitrary set of the top schools at 20? Is there a certain reason 20 is the go to number for the top blank number of schools in the US? I was admittedly uneducated about colleges and rankings up until I got into my first good school, when then I started doing actual research and learned so much including the helpfulness of the subreddit. But I’m still curious about why does everyone talk about a school being t20 and not like t10 or t30, why 20?