It seems like a common notion among casual baseball fans that expansion boosts scoring. Certainly, the individual achievements that have happened in expansion seasons would appear to support this. Every time baseball has expanded, it seems, something noteworthy has happened, be it Roger Maris breaking the home run record in 1961, Mark McGwire doing likewise in 1998, or Rod Carew, John Olerud and Andres Galarraga hitting close to .400 in other expansion years.
Granted, the notion of expansion boosting scoring has its skeptics, most prominently perhaps Bill James who wrote in his 2001 historical abstract:
Expansion favors neither the hitter nor the pitcher, on balance; it does as much to create a shortage of good hitters as it does to create a shortage of good pitchers.
While I trust Bill James more than I trust conventional wisdom in baseball, his claim raised a red flag for me. With the help of the spreadsheet of baseball run averages since 1876 that I wrote about earlier this week, I applied a cursory test.
|Expansion year||League||Average runs per team||5-year pre-expansion average||Difference|
My thought? James is mostly right. Expansion alone won’t create a scoring boon, though it could favor individual achievement since the best players in baseball will face more marginal talents in expansion years. In his 1992 book Baseball’s Last .400 Hitter, SABR member John Holway suggested that in order for someone to hit .400 again, the majors might need to be tripled in size in order to restore player-population ratios of Ted Williams’ era.
That said, the fact that scoring has increased six of eight times that a league has expanded and didn’t meaningfully decrease the other two times is striking to me. I could drill down deeper in my research, though I’ll leave this as is for now.