From SABR member Diane Firstman at ESPN.com on May 11, 2012:
The average number of runs per game per team has fluctuated throughout baseball’s history. There have been declines attributed to better gloves and the introduction of hard-throwing set-up men and closers. There have been increases linked to such things as the lowering of the pitcher’s mound, the introduction of the designated hitter and artificial turf.
Since 1901, the average yearly rate of change has been about five percent either way. … On a team basis, run production can fluctuate from year-to-year based on things as tangible as changes in ballpark dimensions, and as variable as batting average on balls in play. The following table shows the change in run production from 2011 to 2012 for each team, measuring against the average across the majors, with the year-to-year change in performance relative to league average. For example, the Cardinals averaged 4.70 runs per game in 2011, 10 percent better than the league average of 4.28. So far in 2012, they’ve averaged 5.55 runs per game, a gaudy 32 percent better than the league mark of 4.20. So, from year-to-year, they’ve improved 22 percent relative to the league average.
As you can see, the early 2012 season has provided two extreme outliers in this season-to-season variability: the Atlanta Braves and the Pittsburgh Pirates.
Read the full article here: http://espn.go.com/blog/sweetspot/post/_/id/24224/braves-pirates-seek-offensive-history
Originally published: May 11, 2012. Last Updated: May 11, 2012.