LEAGUE RUN-SCORING DIFFERENTIALS SINCE THE INVENTION OF THE DH...

THIS is the time of year when we focus intently on the first scraps of league offensive data, in the obsessive attempt to use tiny sample sizes to make semi-vast pronouncements about the overall health of the game--all prompted by the incursion of the "Statcast Age," which has brought about a strangely strangled shape for offensive statistics. (We admit our bias here, as we sift through the myriad data artifacts for fresh signs of doom; after all, our prognostication of a catastrophic outcome from the still ongoing "launch angle follies" is, like the Wichita Lineman, still on the line: a .225/.300/.390 disaster scenario is still a lingering possibility, if only to prove once and for all what fools these post-neo-sabes be.)

Thus hope for disaster always springs eternal in the spring, and this year is no exception, with a curiously wide divide between offensive production manifesting itself between the leagues. As of early morning (3am) on April 14th, the run-scoring differential between the leagues stood at nearly 17% (4.18 runs/game in the AL, 4.95 in the NL). The AL was hitting .233, with HRs/game actually under one (0.98), while the NL was at a much more robust .252, with 1.1 HRs/game (but with overall SLG still tamped down at levels similar to what was seen in the "pre-Statcast" interregnum prior to the "bombs away" year of 2017).

OF course this stuff always changes, and we all know by now to adjust for the fact that colder early spring weather can wreak havoc on hitters, particularly in the first half of April. But the run differential seemed quite high, and this prompted us to devise a way to map the comparative runs/game performance at a level just granular enough to capture some historical context. And so we did, and so here 'tis, with results that are not dispositive of doom, but laced with a flow and ebb that is unavoidably interesting.

The chart at left shows the run differential in "heat map" mode at monthly intervals (the numbered columns represent April through September...), measured from the AL R/G as compared with the NL. This data covers the twenty-first century, where (as you'll soon see) a remarkable turnaround in comparative run scoring levels occurred even before baseball instituted the odious "universal DH" rule.

Here you can see that up through 2015, the AL was consistently scoring about somewhere between five and six percent more runs per game than the NL. For reasons not yet identified, that changed dramatically the following year, when the differential plummeted from just under seven percent to just over one percent. (The lowest it had been in the twenty-first century previously had been in 2010, when the differential had plunged to just under three percent.)

This newly constricted difference persisted, even in the face of the HR explosion/oscillation that began in 2017. It finally turned negative in 2020, flipped back in 2021, but the institution of the universal DH seems to have tipped it back again: in 2022/2023, the NL was the most robust offensive league by just under 3%.

AND, as noted, the early returns in '24 register a startling difference, with AL down nearly 17%.

Of course, you can see the monthly fluctuations in the data, so what's happening now is clearly in an "ain't necessarily so" state. 2024 might imitate what happened eight years earlier, when the AL was down nearly 13% in April, only to roar back with a mirror-image reversal the following month. But we now have something to track, and we can monitor this differential as the season progresses, to see where it lands.

There are other related stats that can be measured monthly to provide more context for what may be going on since 2015...we'll pull some of that together when we revisit this topic early in June.

TO demonstrate what a sea-change this run differential data actually is, we've reconstructed the monthly data all the way back to 1970 (at right), right before the institution of the DH. In that data you'll see how the DH rule flipped run scoring from out of a significant deficit for the AL (though it didn't take total hold until the expansion year in 1977, which seems to have diluted pitching). From then on, the AL was firmly the higher-scoring league, as the profusion of hot orange in the "heat map" display demonstrates. 

Note, though, that aggregate double-digit differences disappear in 1997, and have not returned since. So there's an historical pattern there; the challenge for us is to determine what (if anything) its meaning may be. In the meantime, stay tuned...