(Photo: Stuart Rojstaczer and Christopher Healy, from the New York Times)

A recent study on college grade inflation has revealed that private colleges are primarily responsible for rises in grade-point averages over the last 50 years, according to an article in The New York Times published Monday.

Stuart Rojstaczer and Christopher Healy, authors of “Grading in American Colleges and Universities” found that college grade-point averages have risen by about 0.1 points each decade from a national average of 2.52 in the 1950’s to around 3.11 in 2006.

The study collated data from 160 schools and found that the average GPA at private colleges stands at 3.3 today, 0.3 higher points than public institutions.

The paper’s authors concluded that the differences in GPAs may explain why students from private institutions appear to be overrepresented in the most selective medical, business and law school programs.