# 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.

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Guest
Nick

Are strike zones being enforced in a similar way to years past or is there an effort to call a smaller strike zone this year?

Member
jfcincotta

I’m sorry, but this is an ill informed use of an inappropriate test for the question at hand. You’re calculating Z-scores to use as evidence that a sample set has a true mean (mu), a process that is completely backward. Even if applied correctly, with your nine degrees of freedom, the 95% confidence interval would be at 2.26 standard deviations not 2, but regardless, is violated by your observation from 2000. In fact, there is less than 1% chance that we get an RS/G of 10.28 in 2000 if there is a true, unchanging, RS/G baseline of 9.35. This should… Read more »

Member
jfcincotta

Arjuna – I know you didn’t explicitly claim that RS/G should remain constant, but the necessary implication in running a t-test is that there is a true mean. The first statement you make, that this is not “that far out of the ordinary,” is a fair point but is in contradiction with any belief that there isn’t a trend. This year’s data point is second furthest out of the ordinary as you define it. It’s less out of the ordinary than 2000, but it’s still more out of the ordinary (further from the sample mean) than any other data point.… Read more »

Guest
Stocktopus

The mere fact that this IS the lowest RS/G in the last decade, would mean this IS the year of the pitcher. I don’t think anyone ever contended that pitchers are having an unprecedented domination of hitters to the extent that it’s a statistical anomaly. I think the phrase “year of the pitcher” fits perfectly with the fact that, yes, RS/G is down compared to recent years and, yes, there have been an odd amount of perfect games/no-hitters. Don’t get me wrong, i’m impressed with the statistical analysis, and i actually found it pretty intriguing. I just don’t think it… Read more »

Guest
jd1234

This seems like a good place to post a theory about why runs are down this year. With the advent and improvement of pitch tracking abilities, I wonder if pitchers are increasingly taking advantage of this new information to exploit the vulnerabilities of hitters. What do you think?

Guest
Rich C

“In conclusion, statistical factors point in the direction of this season being a normal fluctuation in terms of runs scored. ”

No, they absolutely don’t. Statistical factors point that this COULD be a normal fluctuation. Not that it is. That is an important distinction.

Member
jfcincotta

Arjuna – I put your numbers in a spreadsheet and got a different average and standard deviation. Did you use a larger data set to get those two numbers? Additionally, I think Rich C. gets at an important point: you should probably look at this year as a fluctuation from the past and then ask whether this year is likely in context of what we knew ahead of time. We could get pretty Bayesian here, but let’s keep it simple. The first and most important question is: what is a baseline year? To do this, we need a sample set.… Read more »

Guest
Aaron

Isn’t RS/G a measure of pitching+defense? I’m still relatively new to sabermetrics, but wouldn’t a better measure be to subtract out the Defensive Runs per game to get Pitching Runs per game? While I know that defensive metrics aren’t up to par, this would help normalize each year.

Also, it might be good to look at the pooled FIP, xFIP, etc. of all qualified pitchers, weighting by IP and ignoring the constant added per year to scale to ERA.

Guest
Mitchello

Defensive metrics measure a player’s distance above/below average. So for every year, the sum of all defensive runs should be 0. However, I think the decrease in runs scored results more from an increased focus on defense than improved pitching talent.