Another vital parameter: How often does a batter face a righty/lefty pitcher? From the 2007 ABL stats: 78.3% of innings pitched were by right-handers, 21.7% of the IPs were from lefties. I had guessed it would have been about a third lefties.
Another way to figure this is to figure the total splits for 2007 PAs at Baseball Reference. (NL, AL) Can figure the batting sides while we’re at it.
TOTAL NL AL
----- ----- -----
RHP 72.6% 71.8% 73.4%
LHP 27.4% 28.2% 26.6%
RHB 58.9% 60.6% 56.9%
LHB 41.1% 39.4% 43.1%