On June 5th, the Seattle Mariners and the Chicago White Sox played thirteen innings of scoreless baseball before both teams erupted for twelve runs in the last three innings, ending in the sixteenth. On June 8th, the New York Mets and the Miami Marlins played more than two games in one—a twenty inning battle that took over six hours to complete. Only three runs were scored and there was a ridiculously long period—from the bottom of the fourth to the top of the twentieth inning—where no runs were scored at all. The Texas Rangers and Toronto Blue Jays played eighteen the same day. Since June 8th, there have been eleven other extra-innings games, including another eighteen inning game between the Athletics and the Yankees. Recently, one of my friends asked me whether I thought the recent rash of extra-innings games is unusual. Brandon posed the hypothesis that since less and less runs are being scored per game, are more games going to extra innings as a result?

Do you think that all of these extra-inning games are indicative of the trend of the past 2 decades where pitching skill is outpacing hitting skill…I dunno. I may be imagining this, but I think runs scored in baseball have gotten lower in the past 5 years alone and now we’re having a ton of extra-inning games lately.

I thought this was an excellent question and worthy of a bit of research. Let’s start by establishing how many extra-innings games there have been for the past two decades and see if there is any correlation with the amount of runs scored each year.

Above, we’ve got data from the last twenty years placed into a scatter plot with the number of extra-innings games on the x-axis and the number of runs scored on the y-axis. The line running through the middle of the graph is the coefficient of determination, or R Squared. It tells us how predictive the observed data is for future events. An R Squared value of 1 indicates the model is perfectly predictive. In the graph above, the R Squared value is 0.1506, not very predictive at all.

We can say with pretty high certainty that runs scored do not affect the amount of extra-innings games from year to year. But what other factors could affect the number of extra-innings games? Brandon and I looked at two other factors, league average relief FIP and league average Clutch scores. Clutch is a statistic developed by the fine folk at FanGraphs.com that measures “…how much better or worse a player does in high leverage situations than he would have done in a context neutral environment.” Relief FIP could have a correlation if relievers aren’t performing very well and thereby leading to more and more extra-innings games. Clutch will hopefully tell us how well (or poorly) batters are performing in the most important innings of the game, usually the final innings of a close game. To the data!

Not much correlation here either. Reliever FIP is a hair more predictive than straight runs scored with an R-Squared value of 0.1518. That makes logical sense—if the league scores more runs on average, then reliever performance will most likely follow that trend. What I find interesting about the reliever performance is the huge dip in the last three years. League average reliever FIP dropped from 4.21 in 2009 to 3.76 in 2013. We can actually see that the widespread specialization of relievers has had a massive benefit for the later innings.

Clutch is even less predictive than runs scored or relief FIP. That one was a long shot because its not an exact statistic and is only beneficial if we use it to describe the past and not to predict the future. It was designed to be used individually so using league average Clutch was a long shot. Oh well.

Based on these three factors, I think we can safely say that the amount of extra-innings games from year to year is pretty fickle. I think this makes sense, at least theoretically. There are so many things that can lead to an extra-innings game—good pitching, lucky hitting, weather, and on and on—it’s so hard to pin down one factor that can safely predict how many there are each year. That being said, this year is on pace to break the record for extra-innings games which was set in 2011. I wish we could have made a solid conclusion but maybe I’m missing something. If you have any ideas, please let me know. I’m still curious to see why there have been so many extra-innings games this year.