incredible resource

Some of you may know that historical league quality is a bit of a hobbyhorse for me. I've always wanted to be able to quantify the difficulty of all the various leagues through history and throughout the world. Yet the publicly available data on such a seemingly fundamental analytical issue has always been shockingly scarce.

Well this Eric Chalek fellow I've been following who is an expert on translating statistics from Negro Leagues and NPB and the like just dropped an absolute bomb, sharing his league quality data for hundreds of historical leagues. It is the most comprehensive analysis of the issue that I'm aware of by orders of magnitude. I am in the throes of baseball nerd ecstasy right now and just wanted to share this with any similarly-minded folks out there.

Check out his accounting of his system (actually moreso the system of author Scott Simkus who collaborated with Chalek on the project) and the tests they ran on it
Documentation for the file
The file (at the bottom of the page)

This is just a holy freakin grail for me, the most exciting analytical development since...WAR? Like on that scale.

This sounds extremely interesting, I'm going to dive deep into it now. Thanks for sharing, Max!

Great stuff, thanks for sharing Max!

In terms of implications for ATG, this data should assuage concerns about adding cards from the AA, PL, and FL. Even if those leagues weren't quite at the level of the NL, they were substantially better than AAA, and some years the distance from the NL was smaller than the difference between the NL and AL in later years. The Players League was actually the strongest league in 1890! (A finding corroborated by David Gassko's earlier study in one of the links I posted above.)

Perhaps most interestingly, the CUBANS have a strong case as peers of MLB from 1906-30 with more scattered strong showings into the '30s and '40s.

Currently thinking about the figure for the 1961 AL indicating the league was only 88% as difficult as the NL

That squares with the post-integration AL being weaker than the NL because it was slower to integrate, and it led me to check Baseball Reference's replacement levels. Bbref has the number of replacement wins equal for both leagues which confused me for a minute before realizing that the AL had two additional teams and AL teams played 8 additional games! So those two sources are in agreement about the weakness of the 1961 AL. Just think of all the iconic seasons from that year: Maris obviously but also Al Kaline, and career years from Norm Cash and Jim Gentile who never approached those levels again. Totally fascinating to recontextualize all that.

Cool resource