This basic plot shows the fraction of game starts made by left-handed pitchers.
Before making the plot, I had expected this percentage to generally increase over time. That’s clearly not the case.
I’m particularly interested in the major dip starting in 1993. This seems to coincidence with the Steroids Era. Does this suggest that the increase in offense during this period is due, in part, to lack of availability of left-handed starters? Or were fewer left-handed starters used for some other reason?