I figured I wanted to look at whose production increased the most in 1991 and beyond, the first year steroids were "banned" from MLB. In my code, I looked at players who played both from 1985-1990 (a good 6 season sample size) and then looking at any of any of those players who played in 1991 and/or beyond. I cut the PA size off to 1000 PA on both 1985-1990 and 1991-2006. I understand that the years I picked- 1985, 1991, and 2006 are all very arbitrary, but I figured that was my best estimate of baseball when steroid use was at a relative low, when steroid use became rampant, and when steroid use tapered off. I could be totally wrong in my estimates, but I took my best guess.
I then looked at the players' median WAR and wRC+ before and after '91, and then calculated which players had the largest positive difference. Here's my code in case anyone is following along at home.
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Here's the top 43 players with the biggest differences in their median wRC+'s before and after '91
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And lastly, here are all the player's whose median WAR changed by 1 win or more in '91 or later
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What do you guys think of these lists? Again, not a very in-depth analysis, and there are lots of confounding factors and other dilemmas, but it's worth mentioning that 3 of the first 5 players in the wRC+ department all have been connected to steroids, as have 4 of the first 10 in the median WAR change (including Daulton). So what do we think- are Robin Ventura, Kevin Mitchell, and Griffey guilty of juicing?