Where Have All The Stolen Bases Gone?

Back in November, Jack Moore wrote about the return of the stolen base as a valuable offensive weapon. As offensive levels have decreased in MLB over the last few years, the value of taking an additional base has gone up, and the cost associated with giving up an out has gone down, so we’ve seen teams running more often now than they did back when runs were plentiful.

It’s a perfectly logical construct. As hitting is more frequent, running becomes less necessary. When hitting suffers, teams try to find runs other ways to score, and one of the primary ways a team can create additional runs is through efficient base stealing. Base stealing is essentially a substitute good for power, and so SB rates follow a fairly predictable pattern of rising and falling depending on the offensive environment.

Except, that predictable pattern has gone off the rails so far in 2013.

Here’s a chart showing stolen base attempts per stolen base base opportunity since 1993.

Teams ran a lot in the 1990s, as the influences of 1980s-style baseball continued, but then stolen base rates plummeted as home run rates rose and teams began to adjust to a new level of offensive success. The league stolen base rate bottomed out in 2004, and then started to climb again the last few years as the rise in strikeouts pushed offensive levels back down to pre-“Steroid Era” levels. While overall attempts hadn’t quite gotten back to where they were in the mid-1990s, they were close, and seemed to be trending upwards.

Except, that trend has hit the skids in the first three weeks of 2013. The rate of stolen base attempts per opportunity so far this year (5.3%) is basically equal to the 2004 low point (5.2%), and is actually even lower if you look at stolen bases per plate appearance. Clearly, it’s still way too early to be making any kind of broad declarations, and things still have plenty of time to change, but stolen base rates seem like the kind of thing that should stabilize very quickly. For instance, here are the major league SB per PA rates for 2012, by month:

2012	PA	SB	CS	SBA	SBA/PA
April	25,577	418	181	599	0.023
May	32,385	578	196	774	0.024
June	30,589	541	190	731	0.024
July	29,028	545	187	732	0.025
August	32,036	531	188	719	0.022
September	34,564	616	194	810	0.023

The rate of SB per PA in April (2.34%) was nearly a match for the SB per PA for the entire 2012 season (2.37%), and there was hardly any fluctuation from month to month. The old saying “speed never slumps” might not be completely true, but there is certainly a reality that players are either fast or slow, and it doesn’t take a very large sample to determine whether or not they should be attempting to steal on a regular basis. And yet, the entire league has basically put on the brakes this year.

What would explain a dramatic shift back towards fewer stolen bases? Well, higher offensive levels would be the first place to look, given what we talked about above, but it’s hard to find a reason for the lack of steals in overall run scoring. MLB teams are averaging 4.24 runs per game so far in 2013, down slightly from the 2012 total of 4.32 runs per game, which is what we’d expect from the first month of the season. The current runs per game average is lower than any full season since 1992, so the run environment doesn’t look like the culprit here.

Could it be that the league has simply added a number of good defensive catchers and are putting a premium on stopping the running game? Maybe, but the evidence seems to suggest the opposite, actually. Over the last few years, offense from the catching position has been going up, while caught stealing rates have been going down, and the current crop of young catchers includes guys like Jesus Montero and Evan Gattis, who probably would have been pushed off the position by now if defense was the primary variable in selecting backstops.

That trend has continued this year, as catchers are posting a .747 OPS, just barely behind first baseman and left fielders in terms of overall offensive production. It is tough to believe that both offensive and defensive talent levels are rising simultaneously behind the plate, especially given that the caught stealing rate is still just 26%, so the current crop of catchers hasn’t gotten back to throwing out runners nearly as often as they used to. It seems like the trend of giving up some defense behind the plate in order to get more offensive firepower in the line-up is still continuing.

But, if that assumption is true, then the lack of stolen bases is even more mystifying, because a weaker crop of defensive catchers should lead to more stolen base attempts, not fewer. So, maybe it’s all these new fangled “Moneyball” teams and their aversion to stolen bases that are causing the downturn? Well, that theory dies once you realize that the two teams at the top of the stolen base leaderboards for 2013 are the A’s and Red Sox.

So, what’s the deal? I honestly don’t know. Perhaps pitchers have gotten better at holding runners on, and there’s been a league wide improvement in pickoff moves that we haven’t detected. Maybe it’s all just a small sample fluke and this will reverse itself in the near future.

I don’t have an answer here. We’ll just have to keep an eye on the league’s stolen base rates and dig a little deeper to see if there’s an actual structural change that hasn’t yet been identified, or whether this is simply a statistical blip that will be washed away by a larger data set.