## 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.