top20 is more a term rather than the real ranking. Usually it represents the traditionally strong schools. The real ranking could be different every year. I knew at one year, UC Berkeley fell out top 20 in ranking, but it is still considered the top 20 schools. So if you rely on BW or USNEWS ranking, the top 15 usually are a safe bet, but don't put too much weight on schools at the bottom of the list.
West: Stanford, USC, UC Berkeley, UCLA
Midwest: U Chicago, Northwestern, UMich, CMU
East: Harvard, UPenn, Colombia, NYU, Dartmouth, MIT, Duke, Cornell, UVA |