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Baseball is back to reining in stolen base attempts

As home runs have gone up, teams realized that it makes sense to stay below the natural run environment’s break-even point.

MLB: Philadelphia Phillies at Washington Nationals Tommy Gilligan-USA TODAY Sports

We’ve talked a lot about home runs here. Sure, home runs are down slightly in 2018 relative to last season, but they are still up relative to other eras, of course. What is talked about less, I think, is the impact power has had on speed, which was an in-vogue discussion about 40 years ago, as well as right at the start of the live ball era. Yet other than the grumblings of national broadcasters (who people at this site largely ignore), I don’t think anyone serious in sabermetrics has looked at speed and stolen bases as a function of this era.

As I said, this is a discussion that has been around for a while. When the live ball era brought in more home runs; naturally, run expectancy for a runner on first, nobody out, is going to be higher than in the deadball era. In The Literary Digest in 1922, it was asked whether the “most thrilling of baseball plays should be rescued from the slowmoving but iron-bound tendencies of the modern game which are crushing out its very existence?” Even less than a half-decade into the “modern game’s” existence, people wondered whether power would inexplicably tarnish speed.

This push and pull of power and speed was largely neutralized in the 1970s, where the combination of power/speed players revolutionized the game. Subsequently in the actual modern era post-1988, we have seen both an overall decline in stolen bases but a recent push-and-pull in the juiced ball era that I will further document.

When you look at the full history, this narrative makes a lot of sense; the live ball era crushed the existence of the stolen base, only to reemerge and then dissipate from 1980 to the present. This year in particular could be one of the lowest non-strike stolen base totals since those earlier decades.

And very accurately described, the modern era has essentially eschewed the stolen bag, first because of power, and then in the latter sabermetric era of trying to beat back the tendency of attempting more times than it is “worth,” which I will also get to later.

Is this decline attributable to power? Are the modern era’s beefy power hitters really the reason why speed has washed up since the halcyon days of 40 years ago? In many ways, yes:

The better theory posed here is not that home runs and power affect the stolen bases total, but it changes teams’ valuation of stolen bases relative to other offensive indicators, home runs being one of them. Home runs explain 30% of the caught stealing rate largely because if you know more of your players can hit a home run, you’re not risking the out. It’s the same calculation today that managers were making in the 1930’s and 40’s.

If caught stealing then is an indicator of the trends in base stealing, then it would also be helpful to know the break-even point of stealing a base. That is usually defined as the probability of the desired end state times the run value, minus the probability of being caught times the end state run value where he is caught. If we were to make the big assumption that stolen bases are first to second, nobody out (I know it’s a big assumption, but we’re using the back-of-the-napkin here), we could then determine the caught stealing rate relative to that era’s break-even point. Using Tom Tango’s run expectancy matrix, we get the following results from 1950-2018:

This makes even more sense than before. Leading up to the modern era of 1988, teams were stealing more and more in the two decades prior. It got to the point where: a) teams were nearly hitting the break-even point by saturating the league with stolen bases, and b) the league was starting to hit home runs at a rate of increase not seen since the start of the live ball era.

It then got to the point where the steroid era ended, and teams began seeing the value of the steal again as home runs declined. This backfired as teams happily began going past the break-even point, and was subsequently reined in as analytics departments began to flourish, leading us to an era where, sure, stolen bases have declined, but they are at a point where teams’ offensive chances are not being deflated. Speed is nice, but a lower run environment is worse.

We don’t have the run expectancy data on the current season, but I would venture to say that two things are true: one is that while stolen bases continue to decrease, there is still more speed in the modern game than existed from 1920 to 1970, which is nearly half of modern baseball’s history. The second truth is that when it does decline it seems to follow the internal logic of that if other offensive events outweigh the risk of stolen bases, then that option will be largely preferable to the extent it sits below the break-even point. In one sense it is saddening that base stealing has declined, but if the de-juicing continues, we may soon see the calculus change.