How OK is Striking Out?
In the last post, I hypothesized that an increase in strikeouts makes it easier for pitchers to record perfect games and no-hitters. While that might be true, it does not necessarily mean that hitters are faring worse than they used to; it simply means that there are more feast-or-famine days for major league teams. Using data from 1955 up through the current season, I looked at what hitters are doing while at the plate to determine if they are using their plate appearances as efficiently as they can.
In order to do this, I simply looked at how many runs are scored per game and how many strikeouts are recorded per game (shown in the first chart below). The number of runs per game jumped sharply in the early 1990s, just as strikeouts were increasing. Between 1992 and 1993, strikeouts jumped 6.6% per nine innings as runs scored increased by 7.0% per nine innings. Obviously, hitters were doing more productive things in their non-strikeout at-bats.
I then looked at the weighted on-base average (wOBA) of the league from 1955 to 2010. I’ve talked about wOBA before, but to clarify, wOBA averages the run value of each positive action achieved by a hitter; the resulting number is scaled to on-base percentage to make it easier to understand. Therefore, an average hitter has a wOBA near 0.335, a great hitter is 0.400 or higher, and a poor hitter would be under 0.300, just like OBP.
The following chart tracks the league-average wOBA and the strikeout rate of the league for the last 55 years:
During the late 1960s (when the rules had been changed to favor pitchers), strikeouts went up and wOBA went down; when the rules were readjusted to even the playing field, hitters were back to their pre-dead ball era numbers and strikeouts decreased. Beginning in the mid-1980s and continuing through the mid-1990s, strikeouts went up significantly as did the league’s wOBA. This wOBA graph mirrors the runs scored graph, as it should, since wOBA attempts to place run values on each action assigned to a hitter. Until this season (which, as I said in the previous post, is the most offensively-challenged season since 1992), the wOBA and average number of runs scored stayed fairly constant even as strikeouts continued to increase.
The formula for wOBA is as follows: wOBA = (0.72 * NIBB + 0.75 * HBP + 0.90 * 1B + 0.92 * RBOE + 1.24 * 2B + 1.56 * 3B + 1.95 * HR) / PA, where NIBB is non-intentional bases on balls, RBOE is the number of times reached base on error, and PA is plate appearances. So the variables shown are the numbers needed to determine if what hitters are doing something that is counteracting the strikeouts. Here’s a nasty looking chart if you want to see the numbers for yourself.
The first thing I notice is that singles are at an all-time (since 1955) low, supporting the theory that hitters are sacrificing contact in order to drive the ball. Also at an all-time low are triples, though that number has been fairly stable since 1986 and might have more to do with today’s ballparks (I’m a big believer that triples are usually hard hit balls that hit a wall funny or are misplayed; obviously there are stadiums with huge outfields and big alleys for triples, but they are the exception). Hitters are certainly walking more than they did in the 1960s and 1970s, but it’s seen a significant decrease since the turn of the century (3.50 walks per nine innings in 2000 to 2.97 walks per nine innings in 2001). The number of hit batters is up, probably because today’s hitter stands on top of the plate with no fear, some thanks to the body armor they are allowed to wear to the plate. The largest increases have been in home runs and doubles, the latter of which has seen a nearly 50% increase in the last 40 years.
Looking back at the run values for each event, a typical double produces 0.3 more runs than a single and a home run produces a full run more than a single. Strikeouts have gone up, but so have walks (slightly) and hit batters (nearly double in some seasons). The total number of hits has increased slightly, but the extra value in extra base hits more than makes up for the strikeouts.
This exercise showed us basically what we expected; hitters hit the ball less often, but make up for hit by reaching base more on balls not in play (walks, HBP, and home runs). The increase in extra base hits provides more than enough value to make up for the decrease in singles and the overall decrease in balls in play. So even if a hitter strikes out 40+ percent of the time he goes to the plate, he still can be an above average hitter.