WASHINGTON D.C., August 10th – Five no-hitters. Two of them perfect games. A third perfecto lost. And then there was Brandon Morrow, losing his no-hitter with two outs in the ninth. The 2010 season has been branded as the Year of the Pitcher. But statistical evidence points in a different direction.
This chart summarizes the runs-scored data for the 2000-2010 seasons. While the runs scored per game figure for this season is clearly the lowest in the set, there are multiple available factors that determine that it’s a normal fluctuation.
The first is the basic standard deviation. The average of the set is approximately 9.35 RS/G, and the standard deviation is approximately 0.28 RS/G. The z-score column indicates a particular point’s distance from the mean in terms of the standard deviation. Ninety-five percent of the time, a point is expected to be within two standard deviations from the mean, or have a z-score between 0 and 2. As we can see from the chart, the 2010 season fits neatly into that range, with a z-score of approximately 1.7.
The second is the percentile change between each season’s RS/G figure. If we take the absolute value of each percentile change, we find that each year, the runs-scored total differs from the previous year’s total by about 3.81% in one direction or the other. This season hits that mark almost exactly, featuring a 3.79% drop from the previous year.
And there isn’t a definitive trend, either. Of the ten points in the data sent for changes, six were drops from the previous year, and four were increases, leading to the basic average of -1.37%, which equals about -0.14 RS/G over the course of a season.
In conclusion, statistical factors point in the direction of this season being a normal fluctuation in terms of runs scored. We’ve certainly seen dominance from the mound, and this could turn out as being the most pitching-heavy season in recent memory, but it’s well within normal, and could easily go right back the other way at the drop of a hat.