The Rise of Strikeouts

During the week of July 4th, on KJR, Seth Everett and Bill Krueger had a discussion about the rise of strikeouts in MLB over the last decade. They argued that the increase in strikeouts made the game less fun. More strikeouts means less balls in play, which means less athletic feats on defense or the base paths. Basically the rise of strikeouts has made the game more focused around the individual battle between the pitcher and the batter, which is slower and harder to enjoy for causal fans. From there the conversation progressed to their diagnosis of what was causing this rise in strikeouts. Both men agreed it was players chasing homeruns that caused more swings and misses. Their hypothesis got me interested and I started digging into strikeout, homerun, and walk trends over the last ten years.

First let me say, I agree with their original point. The huge increase in the number of strikeouts has made baseball more boring. Strikeouts are not rare or exciting anymore. Innings drag on when every at bat ends with a slow trot, with their head down in shame, back to the dugout. I would much rather see running catches in the outfield or diving stops in the infield. Watching tons of strikeouts every night gets boring.

Here are some stats to back up the rise of strikeouts. In 2016 teams averaged 8 strikeouts per game each. The batters for my favorite team, the Seattle Mariners, averaged over seven strikeouts per game every year between 2010 and 2016. The total number of strikeouts recorded in a season has risen every single year since 2007. There were 32,189 in 2007 and 38,982 in 2016. that is a rise of over 6,000 total strikeouts.

So Messrs. Everett and Krueger were right that strikeouts are raising every year and they are raising quickly. Are they also right that the chase of homeruns is driving the increase in strikeouts? I took a look at homerun totals in every year from 2007-2016. Teams hit 5,610 HR in 2016, the most in the last decade. However, unlike strikeouts HR totals have been a consistent trend. Instead they have been all over the place. The lowest of the last decade was in 2014 at only 4,186. The second highest was in 2009 at 5,042.

After reviewing these numbers I am convinced that the allure of hitting homeruns isn't causing players to strikeout. You can see this lack of a trend in Figure 1 where I plotted the league wide strikeout totals and homerun totals year over year. This plot makes it clear that homeruns aren't climbing at the same rate as strikeouts. Additionally I looked at the correlation between HR and K and found it to be a low positive 0.23. The means HR and K are tied together in a positive direction but only loosely. It is pretty clear to me that if people are striking out more often so they can hit homeruns they should rethink their strategy because homerun totals aren't rising.

Figure 1

 Next I took a look at the walk totals over the last decade. My theory was that maybe people were striking out more and also walking more often because they were just taking more pitches in general. The rise of the value of On Base Percentage (OBP) is well documented. Maybe players were trying to increase their OBP by drawing more walks (BB) and a side effect of this is an increase in strikeouts.

I found something shocking here. Walks are actually trending negatively. They are going the complete opposite way of strikeouts. In 2007 there were 16,079 BB. In 2016 there were only 15,088. Walk totals dropped every year between 2009 and 2014. They bottomed out at 14,020 in 2014. In that same year the league struck out the third most times in the decade. Figure 2 plots walk totals and strikeout totals every year between 2007 and 2016. You can clearly see the two trends are opposite. Additionally the two are barely negatively correlated at only -0.13. If players are striking out more often in an attempt to draw more walks they are failing badly.

Figure 2

 This all leads me to believe that the cause for the rise of strikeouts isn't related as much to the batters as it is to the pitchers. I think that the quality of pitching has been steadily increasing over the last decade and hitting has kept up. We already saw that strikeouts have risen and walks have dropped. It is easy to see how both of these phenomena could be attributed to increased pitching skill. Additionally the average fastball velocity in MLB has increased from 92 MPH in 2007 to 93.5 in 2016. Figure 3 shows the year over year change in average fastball velocity. Upping the speed of pitches makes hitting more difficult.

Figure 3

 Anecdotally the increase velocity can be seen by looking at the Seattle Mariners pitching staff. This year the Mariners have three relievers (Diaz, Altavilla, and Pazos) and one starter (Paxton) averaging over 96 MPH on their fastballs. It isn't shocking to see guys up near triple digits. In fact it has become the expectation that your relief pitchers are flame throwers. Guys who can't hit 95 need not apply for late inning relief.

Strikeouts have clearly risen over the last decade of major league baseball. The increased rate of guys failing to put the ball in play is making the game less fun to watch. The culprit for this hitting ineptitude doesn't appear to be batters chasing HR or trying to draw walks. Rather the overall talent of major league pitching has  steadily increased. Teams are featuring more hard throwers making it harder to put the ball in play. Batters have failed to keep pace with the quality of pitching in MLB which has resulted in more strikeouts and less walks and homeruns.

Sources: Fangraphs, Baseball Reference