[grmagne]

I ran a simulation of a 16-team major league with five minor leagues: R, A-, A, AA, AAA. It went through dynamic expansion early, so there are actually 20 major league teams and 100 minor league teams through most of the simulation. The league ran from 2005-2060 but I only counted 2015-2060 because I wanted the minor leagues to have drafted players rather than inaugural draft players.

The league database has an enormous sample size: 207,674 player-seasons of hitting stats across 6 levels of play and 46 seasons, plus 119,092 player-seasons of pitching stats. Nobody’s going to convince me I don’t have a large enough sample to reach these conclusions.

I’ve attached a chart below that shows the number of left-handed & right-handed pitchers that appear at every level in the simulation as well as their composite ERA. The interesting thing is that lefty pitchers always have noticeably worse ERAs than righties at every level except the Major Leagues. I think what’s happening is that a typical minor league team has more right-handed batters than left-handed batters and minor-league managers rarely use platoons. So RHPs get an advantage by facing more RHB while LHPs are facing basically the same lineups, except at a platoon disadvantage. That must be causing the ERA differences, because over a 46-year simulation LHP had a 0.14 to 0.17 higher ERA in the minor leagues, and this difference was consistent across every minor-league level.