Ken writes:

Home runs per game for September currently stand at 0.80. August was the 129th straight month of at least 0.83 HR/G, so September could very well end up with the lowest rate in a month since April 1993. Prior to that, below 0.80 was commonplace, occurring for example 17 times in the 24 months from April 1989 to September 1992.

That’s home runs per team game. I use home runs per game, so just double all those numbers. I’ve checked the numbers and Ken is right. Looking at months with at least 60 games, September 2014 is turning out to be the lowest average home runs per game month since April 1993. While 1993 is considered to be the start of the high offense era, four of the six months that season were at 1.80 HR per game. The first time HR fell below that mark after 1993 was in April of 2008, at 1.78 HR per game. It would not happen again until May 2011 and remained below 1.80 through July. July of 2013 was down, the only month in 2013 below 1.80, but May of 2014 is the only month this season above 1.80. We still have not reverted back to 1992, however, in which every month was below 1.60.