baseball-reference.com umpire data is confusing.

All parks symmetrical: 1972-1989 NL. Then v. Now. Saturday, February 6, 2016

2015 plate umpire differences will be examined in a future post. The way in which baseball-reference.com displays umpire data for recent seasons is EXREMELY confusing. I've sent an inquiry to baseball-reference.com but have not received a reply yet. See the next post for more on this.
_______________________

The message was sent to bugs_1@sports-reference.com as well as a link to this post.

I finally opened three separate browser tabs to try to see what the heck was going on:

2015 National League Pitching Splits
2015 American League Pitching Splits
2015 Major League Baseball Pitching Splits

The "League" tabs each have one set of pitching data for umpires, same as for NL seasons 1972-1989. For the previous post I used NL data for 2015.

Later I looked at 2015 MLB umpire data. It has FOUR seemingly mutually exclusive groups of umpires. Using the group with the most MLB umpires I got this summary data:

Ump Hi	Ump Lo	Ump Hi	Ump Lo	Year	Ump%dif	Ump%dif	% dif	% dif
SO/W	SO/W	SO9	SO9	2015	SO/W	SO9	ERA	HR/AB
3.98	1.91	9.0	6.7	NL	108.38%	34.33%	-9.36%	-4.85%
4.07	1.91	8.7	6.2	AL	113.09%	40.32%	-12.14%	-7.22%
3.92	2.11	8.5	6.8	MLB	85.78%	25.00%	-10.61%	-6.11%
???	???	???	???	MLB	???	???

Notice that the hi/lo data for MLB does not make sense relative to that for NL and AL, which have data for individual umpires for each league respectively. For instance, an umpire may have worked 10 NL games and 20 AL games. Then all 30 games are the "master" group in the MLB tab. But there are other umpires who are not included in that master group but in one of the other three smaller umpire groups. None of these groups are defined.

I mention all this in case the comments concerning 2015 NL umpire data in the previous post are inaccurate. When/if that is determined, clarification will be posted.