RSI

From Wiki Gonzalez

RSI stands for Run Support Index, and represents a pitcher's run support, adjusted for park and era. It was invented by Chris J, who gave a presentation on it at the 2004 SABR convention.

Here are the steps:

1. Go to Retrosheet and find out how many runs a team scored for a pitcher every single start he had in a given season.
2. Add those numbers together and divide by games started. That's his run support per game.
3. Take that number and divide it by his team's batter park factor for that season (available at Baseball-Reference.com). This adjusts his run support for his home park.
4. Now divide this number by the league's R/G average and multiply by 100.
5. For single-season totals, round off to the nearest integer.

A pitcher with perfectly average run support will have a Run Support Index (RSI) of 100. 10% higher should be 110, etc.

For career numbers, take each individual season's RSI, multiply it by GS, add those together for every year the pitcher played in, & divide by career GS. Round to the hundredths decimal.

There is also a formula to adjust W/L records based on RSI.

RSI is used by many posters in the Hall of Merit, though almost never on Primer itself.