So...we have shameless generated a month-by-month log of run scoring per game per team, summed up into each league, that goes back to 1901--it's interesting data, though semi-vulnerable to the slangy arrows of feckless young quants (following the lead of flatulent old quants who should've been forced to do something else for a living...) sullenly alluding to "sample size issues." Don't let that deter you from perusing it anyway, as it provides fascinating topographic perspective of run scoring, its range of fluctuation, and--perhaps most intriguingly--the oscillating differences between the two leagues as captured in many snapshots (a total of over seven hundred on the full chart, in fact).
Now naturally we're not going to print that whole darned chart here--the BBB blog format is more than a bit unforgiving with such visual excess--but we'll give you a slice that portrays the last fifteen years. (That's what they used to call a "free sample" before everything became "bait and switch.") Here 'tis:
Now what you have here are R/G by month for each league, plus the difference between the leagues for those monthly values, from the tail end of the long offensive explosion that ran from 1993-2009 all the way up to this year.
All monthly R/G values of 5.00 or more are shown in bold type; those monthly values under 4.00 are shown in red. The highest monthly R/G value for each year in each league has a bold box around it.
This is, as our friends in the cereal industry like to say, a more granular level of run scoring data, showing fluctuations and some patterns for each league year as it plays out. The color-coding tells us that the NL had the most serious run-scoring downturn in the past fifteen years, with that situation becoming chronic from late 2012 through mid-2015.
What the figures in blue show, however, is not a lot of real difference in R/G between the leagues over recent years. (You will have to trust us for now when we say that this was less the case in other periods of baseball history--the 1920s, 1930s, and 1980s, for example.) We've bolded the differentials of three-fifths of a run (0.60) or more; until we ran into some kind of buzzsaw last month (that's June '21 for those of you keeping score at home...), we had not had a league differential that high since 2011. (Note that the darker shade of blue indicates when the NL had the higher R/G value: eyeballing that pattern will indicate that this is a relatively rare occurrence.)
In 2019, the egregious "homer explosion year" (hopefully an all-time record that will never be seriously approached again) did not produce serious run differentials (four of the six months showing a difference of less than a tenth of a run either way). And that was representative of what we'd seen since September 2011.
But in 2021, as noted, something shifted last month. After two months of relative run-scoring parity, we had a notably divergent June thanks to an AL homer surge (1.39 HR/G) pushing them back over 5.00 R/G, while the NL languished at its same lower-than-historical lifetime run-scoring rate, with its HR/G rate remaining steady at around 1.1 . That run-scoring delta (0.67) could be a transient phenomenon: they often are. The very early numbers in July, however, seem to suggest an even bigger separation (those figures shown in grey).
In our most recent post we suggested that the game be overhauled into three leagues based on run scoring levels; for the moment, at least, it looks as though baseball is trying to take us up on at least a portion of that idea. (We still think breaking up the leagues is the best approach for the game in the long run, but performing such upheaval on such an essentially conservative entity such as baseball is a long shot.)
How long will this run divergence last? There is a tendency for this phenomenon to persist once it manifests itself: a look at the full chart (as noted above) shows such a pattern as recently as the 1990s. Another era of bifurcation may well be upon us--stay tuned...
