GPA

From Wiki Gonzalez

GPA is short for "Gross Production Average", a statistic thrown together by blogger Aaron Gleeman, the formula for which is:

((OBP * 1.8) + SLG) / 4 = GPA

It was briefly called "Gleeman Production Average". It's frequently used at The Hardball Times, having the advantages of being more accurate and easier to understand than OPS, and easier to calculate than EQA. It can also be used for splits, something EQA is not available for.

The basic math was actually inspired by TangoTiger, who analyzed the relative worth of OBP and SLG in his article "OPS Begone" and concluded that OBP is roughly 80% more valuable than SLG. Gleeman took the extra step of dividing the sum of the two by four to mimic the Batting Average scale.