Home > MLB, Stats > Extra Inning Affairs: Occurring at a Greater Rate than Ever Before?

Extra Inning Affairs: Occurring at a Greater Rate than Ever Before?

On Saturday, June 4th, 2011, Matt Kemp of the Los Angeles Dodgers hit a grand slam in the 8th inning off of Cincinnati Reds Pitcher Logan Ondrusek to send the Reds and Dodgers to extra innings at Great American Ballpark in Cincinnati.  This was of great significance to a struggling and maligned Dodgers offense.  But was also more significant is that Kemp sent the Dodgers and Reds to Major League Baseball’s 100th extra inning game this season.

The 100th time that two teams and four umpires were sent to extra innings this year came on the day where MLB played its 870th game of the season, which is 36% of the way through the full season schedule.  So it’s still early, and a lot can change very quickly.  But I felt like, for sure, this season was featuring a higher rate of extra inning affairs than any other recent MLB season.  So I ran the numbers, and this is what I found:

Year	% X-Inn MLB R/G
2011	11.49%	4.21
2010	9.05%	4.38
2009	8.02%	4.61
2008	8.57%	4.65
2007	9.05%	4.8
2006	7.62%	4.86
2005	7.49%	4.59
2004	8.98%	4.81
2003	8.11%	4.73
2002	8.25%	4.62
2001	8.03%	4.78
2000	8.32%	5.14
1999	7.87%	5.08
1998	8.52%	4.79
1997	8.65%	4.77
1996	9.62%	5.04
1995	8.93%	4.85
1994	8.94%	4.92
1993	8.64%	4.6
1992	9.97%	4.12
1991	10.46%	4.31

source: baseball-reference.com

This shows the run environment alongside the percentage of games that took longer than 9 innings to decide.  X-tra inning games are happening more in 2011 than at any point in the prior 20 seasons, and by a substantial margin.  The last time that more than 10% of games went to the 10th inning happened in 1991  Furthermore the correlation between the current MLB run environment and the percentage of games that go longer than anticipated is fairly clear from this exercise.  When more teams score more runs, a higher percentage of games get decided in nine innings.  That is fairly straightforward.  The Kemp game is an anomally: grand slams in regulation typically do not take us to extra innings, they usually decide the game.

Of course, beyond the trend between run environment and extra innings, its far more difficult to establish a clear trend that we’re seeing more extra inning games now than ever before.  Let’s take that table above, and throw out the 2011 and 1991 lines.

Year	% X-Inn	MLB R/G
2010	9.05%	4.38
2009	8.02%	4.61
2008	8.57%	4.65
2007	9.05%	4.8
2006	7.62%	4.86
2005	7.49%	4.59
2004	8.98%	4.81
2003	8.11%	4.73
2002	8.25%	4.62
2001	8.03%	4.78
2000	8.32%	5.14
1999	7.87%	5.08
1998	8.52%	4.79
1997	8.65%	4.77
1996	9.62%	5.04
1995	8.93%	4.85
1994	8.94%	4.92
1993	8.64%	4.6
1992	9.97%	4.12

Here we see that the trend is actually way more clear when we throw out the numbers from 2011 and from 1991: the percentage of extra inning games in baseball is actually going down, substantially, over the last 20 years.  The outliers in the data include any time that more than 10% of baseball games go to extras in a season.  It is unlikely, given the recent sample, that more than 10% of games will go to extra innings over the rest of the season.

There is one qualification I need to make on that: it’s not unlikely that we can see all time highs for extra inning games this year IF offensive levels continue to drop over the next four months.  That in itself is unlikely for two reasons: natural offensive regression, and the warmer weather in the summer typically offering a bump to offensive totals.  But it’s been an odd MLB year to date to say the least, so it’s at least possible that offensive totals could fall between now and September.

This run environment is NOT a historical outlier with regard to producing a higher rate of 10th innings.  The outliers in this data set actually occurred when runs per game in baseball were over 5, most recently around the turn of the century (1999-2000), and also immediately post-strike (1996).  Based on the last 20 years, there should have actually been fewer extra inning games in those seasons, but, relatively speaking, there were many.

I can conclude from this research that in the last twenty years, extreme valleys in offensive numbers have created more extra inning games, which is a primary reason that we have seen a spike in long games when the run environment dips below 4.3.  But the overall trend in MLB has been away from extra innings, at least in the last 20 years.  Clearly, there are other factors at play here besides run environment on extra inning occurrences; factors that have been causing more and more games to be decided in 9 innings.  I will revisit this at the end of the season, and try to address what else is causing the downward trend in extra inning games, and whether or not circumstances have changed now in the 2011 MLB season.

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