Hello, Here is the latest data I could find. Semester system including early semester 63%, Quarter System 23%, Trimester 2%, 4-1-4 system 7% and not indicated 5%.
This data is from The AACRAO (group of admssions officers) 1993 report by Orville Walz. This was futher confirmed in part by Alan Bright who in 2002 reported Quarter system to be about 22.2%. It looks like colleges rarely change there system since the early 1970's and were only changing at a rate of .2% a year. Hopefully this helps. Thanks Tom Please click accept.