Year of the Pitcher?…Think Again
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.
| RS | RS/G | Z-score | Change | Change% | ABS % | |
| 2000 | 24971 | 10.28 | 3.34 | N/A | N/A | N/A |
| 2001 | 23199 | 9.55 | 0.72 | -0.73 | -7.10 | 7.10 |
| 2002 | 22408 | 9.22 | 0.46 | -0.33 | -3.46 | 3.46 |
| 2003 | 22978 | 9.46 | 0.40 | 0.24 | 2.60 | 2.60 |
| 2004 | 23375 | 9.62 | 0.97 | 0.16 | 1.69 | 1.69 |
| 2005 | 22326 | 9.19 | 0.57 | -0.43 | -4.47 | 4.47 |
| 2006 | 23599 | 9.71 | 1.30 | 0.52 | 5.66 | 5.66 |
| 2007 | 23322 | 9.60 | 0.90 | -0.11 | -1.13 | 1.13 |
| 2008 | 21939 | 9.03 | 1.14 | -0.57 | -5.94 | 5.94 |
| 2009 | 22419 | 9.23 | 0.43 | 0.20 | 2.21 | 2.21 |
| 2010 | 14813 | 8.88 | 1.69 | -0.35 | -3.79 | 3.79 |
| STDEV | 0.28 | -0.14 | -1.37 | 3.81 | ||
| AVERAGE | 9.35 |
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.