In the last 50 years, grade inflation has been prevalent in both public and private institutions of higher education.

But private schools have far outpaced public schools, according to a new study.

In the last five decades, college grade-point averages have risen approximately 0.1 points per decade, from a national average of 2.52 in the 1950s to about 3.11 in the mid-1990s.

The study, by geophysicist Stuart Rojstaczer and Furman University computer science professor Christopher Healy, uses historical data from 80 four-year colleges and universities.

What the researchers found is that grades at public and private schools rose for the most part in tandem in the first half of the 20th century.

But then private school students began receiving significantly higher grades than peers with similar scores on standardized tests such as the SAT.

Based on data from 160 schools, the average GPA at public colleges and universities is now 3.0. At private schools, it is 3.3.

But what's most interesting about this report is how those differences affect students' career paths in industries where grades, not experience, are valued highest.

The New York Times puts it best:

The authors suggest that these laxer grading standards may help explain why private school students are over-represented in top medical, business and law schools and certain Ph.D. programs: Admissions officers are fooled by private school students’ especially inflated grades.

More points from the study:

Science departments now grade, on average, 0.4 points lower than humanities departments,

Science departments now grade, on average, 0.2 points lower than social science departments.

Relatively lower grades in the sciences discourage American students from studying such disciplines.

The authors write that this has implications for our international student body:

Partly because of our current ad hoc grading system, it is not surprising that the U.S. has to rely heavily upon foreign-born graduate students for technical fields of research and upon foreign-born employees in its technology firms.

The real issue at hand? Schools continue to believe that granting higher grades gives their alumni advantages.

Want more information? The authors' GradeInflation.com website has a wealth of charts and graphs for the data used in their study, as well as listings of data by school, from Harvard and Yale to Albion and Spelman.

The authors also have several sets of college rankings.

This post was originally published on Smartplanet.com