Stolen Base Strategies Through History
This week's subject is a little lighter fare, focusing on how the stolen base has changed through time, and whether there is any rhyme or reason to why that has occurred. The amount of stolen bases has fluctuated throughout history. The early days of baseball saw a lot steals until the live-ball era began. As teams started scoring more and hitting more home runs, the speed game went on the decline, picking up again as scoring decreased throughout the 1980's.
A major explanation for the difference in stolen base strategies is that teams were rationally reacting to run environments. As scoring became harder, teams played "small ball" in order to scratch out runs. The goal here is to find out if teams actually did this and whether it was a rational strategy.
First, the relationship between runs and stolen bases. One would think that stolen bases would increase as run scoring decreased. Is this the case? According the above scatter plot, we see a very tenuous relationship. The points out to the right are deadball era years, where stolen bases are high. However, contrary to popular perception run scoring wasn't all that low during the deadball years. The relationship isn't any stronger after 1920 either - the rest of the scatter points are basically in a big clump. That pretty much puts to rest the myth that stolen base trends are a reaction to run scoring.
But is there another relationship between offense and stolen bases? Indeed, the graph above shows the relationship between steals and home runs over time. As you can see, steals and homers seem to be inversely related. Meanwhile, it doesn't have much of a relationship with scoring. A scatter plot doesn't tell quite as strong of a picture, although it's very easy to identify various eras based on these two statistics, which is something that I found pretty cool, even though it wasn't the point of the study.
It would make sense that teams would limit their steals when run scoring was high, but it might make even more sense when those runs are coming via the longball. Obviously, there's no point in taking an extra base if you're likely to be knocked in with a homerun anyway.
The real test of looking at the value of the stolen base is the break-even point. How often must a stolen base attempt be successful, before it is a good play? And how did this breakeven point change over time? Using Tom Tango's Run Expectancy Generator (which didn't do a perfect job across eras mainly because of differing error rates, but it's close enough) I calculated the break-even points on a no-out steal of second base. Obviously there are other situations in which a steal takes place, but being a common one, it's reasonable to use this as a baseline for how advantageous the stolen base is across eras. Picking the most typical point in each of the eras above, and tossing in anomalies 1968, 1930, and today, we can see that while the breakeven point has changed some, there's not a huge difference.
Obviously looking at the break-even rates, we would expect that the number of steals would be highest in the dead-ball era and in 1968. While steals were higher in the dead-ball era, the number of stolen bases in the 1960's was eclipsed by the 1980's and even the current era, which has much higher scoring. While stealing was a better proposition in the 60's, it was used as much as it is today.
Of course, there is a final factor that comes into play: the likelihood that a stolen base attempt is successful. I can't think of much good reason for why the stolen base success rate would change over time, but the fact is that it has changed dramatically. Modern base stealers are vastly more successful than they have been in the past. Why this is, I'm not sure. Perhaps players are faster now, without a corresponding increase in catcher arm strength and accuracy. Perhaps teams are better at reading and timing pitchers' moves to the plate. Or perhaps teams are just better about stealing bases they know they can make. In any case, the chart below combines the data.
As you can see, the stolen base success rate varied tremendously over time. The variation here is far more than the variation in the break-even rate. Hence it would make sense that teams would steal more bases today than in the past. Certainly there is more stealing in the modern 1974-2009 era, than there was between 1930-1973. However, the odd scenario is the deadball era and the 1920's, where stealing was still prevalent, despite abysmal success rates. In the 1920's stealing was about as lucrative as it is today, but with about a 55% success rate vs. a 73% success rate. Nevertheless, stealing was a common tactic.
Looking at the data as a whole, there's not a lot of rhyme or reason about why some eras are high stolen base eras and others are not. The rate of stolen base tends to go up and down without any real correlation between rate of success or strategic value. Part of the problem seems to come from the fact that homeruns seem to be the biggest determinant of whether teams steal or not.
However, home runs don't have a major impact on the breakeven rate. Using today's data, I kept the number of runs constant but doubled the number of homers. The breakeven point went up, but slightly (from 81.0 to 82.9). Similarly I brought the number of home runs down to zero (keeping scoring constant), and the breakeven point again changed very slightly (from 81.0 to 80.5). With the breakeven point barely moving despite dramatic differences in homerun rate, using homers or lack of homers to justify base-stealing strategy isn't a good move. However, I have a feeling that if home runs dropped precipitously today, teams would begin to employ vastly more basestealing - likely an irrational move. More important to a team's strategy is the run-scoring environment, no matter how the runs are scored.
In conclusion, baseball teams have behaved irrationally with their base-stealing strategies through history. It seems that steals have been a function of homers, or simply fashion, and not based on the actual value of the steal. But did you really expect John McGraw to have read the Hidden Game of Baseball?