When I was growing up, my father, in an effort to increase my chances of making the major leagues, would make me do things left-handed. It started with small things like using the television remote, washing the dishes or clipping my fingernails (that one was tricky), but eventually it got to the point where he would burn my right hand to keep me from using it.

OK, so none of that is true (relax, Mom). But it has been true throughout baseball history that left-handed people have a spectacularly better chance than the rest of us of reaching the major leagues. Worldwide, the percentage of people who are left-handed is somewhere on the order of 4%, but in baseball the percentage is much, much higher. Left-handed batters (who aren’t necessarily left-handed people) enjoy a positive bias because they are more rare and because they typically have a positive platoon split against right-handed pitchers, a group that forms the majority of hurlers. Likewise, southpaws are prized because they can reverse that advantage.

In the last 10 years, though, the percentage of batters faced by left-handed pitchers has dropped off dramatically:

This graph might be a little misleading, since it’s blown up to the 20-40% range, but considering the stability until about 1992, the change is dramatic. Despite the roughly 4% increase in the last two seasons, southpaws are facing fewer batters now than they have for more than 20 years.

There are several possible explanations for this. The first was that there was a preponderance of star left-handed pitchers in the 1970s and ’80s who have been replaced by star righties in the 1990s and 2000s. Of course, there were plenty of star right-handers during the 1970s and 1980s and there are plenty of top flight left-handers (Randy Johnson, anyone?) who have been dominating the game for the past decade. Furthermore, since the decline is in batters faced and not necessarily performance against those batters, it makes sense that perhaps the fault would lie more with the inning-eating middle class of left-handed pitchers.

By breaking pitchers each season into three groups–pitchers who throw between 10 and 100 innings, 100 and 180 innings, and 180 innings and above–we can quickly test this theory. The percentage of left-handers drops significantly in all three groups. Rather than being the result of a few retiring stars, the decline of the lefty is occurring across the board. Therefore, it’s more difficult to isolate reasons like the increased specialization of the left-handed reliever from the retirement of a few star left-handed workhorses.

Instead, the reason may lie with the inherent advantage of being a left-handed pitcher: facing left-handed batters. In fact, given that the majority of major-league hitters bat right-handed, southpaws are at an inherent disadvantage. If the group against which they are specifically employed to dispatch is either performing better against them or decreasing in size, demand for their services decreases. Simply, if there aren’t any left-handed hitters, who needs left-handed pitchers?

Here are how the percentage of plate appearances have broken down among left-handed, right-handed, and switch-hitting players over the last 32 years:

Now, we might be onto something. While the playing time allocated to both right- and left-handed batters decreased from the ’70s to the early- to mid-’90s, the number of switch-hitters increased (before tailing off a bit recently). This trend has the interesting effect of increasing both the number of right-handed batters and the number of left-handed batters. For a while there, it looked like we were drifting towards a platoon-split-free world. (Oh, to dream! Stay in the dugout, Tony La Russa!)

Unfortunately, this still doesn’t answer our question since the number of solely left-handed hitters is, in fact, almost exactly what it was 32 years ago. Instead, let’s look at the usage of pitchers and hitters as the years have passed:

This a breakdown of the various bats/throws matchups over the seasons. The top, and most common, line is right-handed batters versus right-handed pitchers. The next most common is LHB v. RHP and so on down the line. What’s interesting about this is that instances of LHPs facing RHBs have been steadily decreasing over the past 30 years. While this has been going on, the number of switch-hitters facing right-handed pitchers has dramatically increased, much more so than the number of switch-hitters facing lefties.

Looking at the three lines that pertain to RHP, we can see that RHPs are facing more RHBs (after a dip in the early 1990s), more switch hitters, and about the same number of left-handed batters. Southpaws, however, are facing steadily fewer RHBs, fewer switch hitters since about 1991, and about the same number of left-handers. These trends point to the idea that left-handers are being used in a more specialized fashion.

Likewise, here are the percentage of batter/pitcher matchups that feature players performing with the same arm or different:

As the blue line–indicating left-left or right-right matchups–increases, the advantage moves increasingly towards the pitcher. Consequently, the decrease in different-sided matchups over the last 10-12 years should take away some of the advantage from the hitters. Much of the enormous bulge in the middle of this graph can be attributed to the massive increase in switch-hitters in the ’80s and leading into the ’90s. However, there has clearly been a market correction, as of late as the lines are moving back towards the center.

To some extent, the correction of late can be attributed to the decrease in switch-hitters, which peaked in the late nineties, well after matchups began trending back towards their early-1970s numbers. Without switch-hitting to blame, if the number of same-sided matchups is increasing, the number of plate appearances going to LHBs is steady, and the number of batters faced by left-handed pitchers is going down, that can only mean that left-handed pitchers are being used in more specific roles. Everyone who’s sat through a four-pitcher inning lately could have figured that out, but what’s not really obvious is the fact that it’s costing southpaws their jobs and their playing time.

It’s not unlikely that baseball is still correcting for the increase in switch-hitting that peaked in around 1997 or 1998. Since, as mentioned, southpaws draw most of their advantage and subsequent job opportunities from performing against the minority of left-handed hitters, an increase in hitters who are not susceptible to that advantage would cost quite a few pitchers their jobs. Given the slight increase in solely left-handed batters in the past five years, more LHPs will be needed more often, so their percentage of the playing time should increase over the next few seasons.

For now, however, all of you righties who are trying to throw left-handed to make the big leagues…maybe you should try hitting instead.

For those of you who e-mailed me after my last
, my laptop died shortly thereafter and dragged many of your e-mails down to the grave with it. If I didn’t respond to you, please feel free to e-mail me again and I’ll be happy to answer your questions. Sorry for the inconvenience.