Record First Half HR Percentages In Both Leagues

Using the Baseball Reference Play Index, I found HR/PA and HR/AB for both leagues. I selected the option that show only first half numbers. So this compares the first half so far this year with the first half of all other years. These numbers here are through Wednesday's games. Of course, we are just short of the All-Star game, but these figures probably won't change that much in a few days. Also, the the first half is not the same number of games in each season. But it is better to compare the first half this year to the first half of other years instead of entire seasons.

For PAs, I included all of them. Sometimes I like to take IBBs out but we don't have them for all years. Something similar for the breakdown of sacrifice hits into sacrifice flies and sac bunts.

In the AL, the HR/PA rate is about 6.8% higher than the next highest year (2017). For HR/AB, it is 7.0% higher. In the NL, those numbers are 9.4% and 7.6%, respectively.

Here are the top 10 seasons for the AL:

Year	HR/PA		Year	HR/AB
2019	0.0363		2019	0.0406
2017	0.0339		2017	0.0379
2000	0.0331		2000	0.0375
2016	0.0319		2016	0.0354
1987	0.0313		1987	0.0353
2018	0.0311		1996	0.0352
1996	0.0309		2018	0.0347
2006	0.0299		1999	0.0338
1999	0.0298		2006	0.0335
2009	0.0293		2009	0.0330

Here are the top 10 seasons for the NL:

Year	HR/PA		Year	HR/AB
2019	0.0351		2019	0.0394
2017	0.0321		2000	0.0366
2000	0.0320		2017	0.0360
2001	0.0301		2001	0.0341
2016	0.0289		1999	0.0327
1999	0.0287		2016	0.0324
2018	0.0285		2018	0.0321
1955	0.0279		1955	0.0316
2003	0.0279		2003	0.0315
2006	0.0277		2006	0.0313