There has been a lot of discussion and speculation why the HR totals in 2016 were so high. Many have claimed that the ball must be juiced, despite, AFAIK, complete lack of evidence. MLB also has denied the juicing, and I can't think of any motive for them to lie about this. I thought I would try to investigate.
I looked at the avg MLB stats for the standard batting categories from 2000 to present to see if I could tell anything. HR totals have bounced up and down during this period, w higher totals before PED testing started in 2003 and especially higher totals before the advent of pitch/Fx in 2007. HR totals, as well as Runs totals, reached a low point in 2014 (4186 & 19761), and have risen dramatically in each of the last 2 years (4909, 5610 & 20647, 21744), w 2016 HR totals being the highest since 2000, which was in the prime of the PEDs era. Offensive stats in general decreased steadily from 2007 to 2014 but HRs have bounced up and down during this period. 2014 seems even more peculiar than 2016 in that there were far fewer HRs that year than any other year that I looked at (never heard anyone claim that the ball was deadened that year, tho). The 2014 Runs total was the lowest, too, but not by nearly as much as HRs. The dramatic rise in HR and Runs in 2015 seems not so much a surge in offense as it was a return to the mean from the unusually low totals of 2014.
I thought that batted ball data might provide some possible answers. It stands to reason that higher hard contact rates, higher pull rates and higher fly ball rates might account for the HR surge. I looked at MLB batted ball data back to 2007. Hard contact % did rise in 2016 but so did soft contact as medium contact declined. There were even more dramatic rises in hard contact rate from 2009 to 2010 and from 2011 to 2012. HRs did rise dramatically from 2011 to 2012 but actually dropped dramatically from 2009 to 2010. Pull rate also rose in 2016 but actually was higher in 2014 when HRs were at a recent historic low. Pull rates havent seemed to vary much in this period, never changing by even as much as 1.5% year to year. Hard/Medium/Soft contact rates have bounced up and down. I'm not sure how much I trust the contact statistics because in 2011 hard contact rate was dramatically lower and soft contact was dramatically higher than any other year before returning to more normal levels the next year. The HRs and Runs that year were rather low but not nearly as low as 2014 which had normal hard and soft contact rates. Fly ball rates are down somewhat in the last 5 years and line drive rates are up some during this time. The 2016 FB rate was up a bit but both the FB and LD rates were virtually the same as the historically low HR year of 2014.
My conclusion from this is that the 2016 HR rate is probably mostly random variation, w possibly some help from the increase in hard contact. I would expect that it will regress to a more normal figure for the pitch/Fx era, which is an average of 4834, which is very close to the 2015 total.
A few other interesting items: Strikeouts have increased every year since 2005. Walks have gone up and down and then up again the last 2 years, but are about the same now as they were in 2005. Runs have gone down every year since 2006 before increasing the last 2 years. Interestingly, the average age of MLB players has gone done or stayed the same since 2004, decreasing from 29.3 to 28.4 during that time. Perhaps this is because of careers being shortened by the discouraging of PED use brought about by testing.
I looked at the avg MLB stats for the standard batting categories from 2000 to present to see if I could tell anything. HR totals have bounced up and down during this period, w higher totals before PED testing started in 2003 and especially higher totals before the advent of pitch/Fx in 2007. HR totals, as well as Runs totals, reached a low point in 2014 (4186 & 19761), and have risen dramatically in each of the last 2 years (4909, 5610 & 20647, 21744), w 2016 HR totals being the highest since 2000, which was in the prime of the PEDs era. Offensive stats in general decreased steadily from 2007 to 2014 but HRs have bounced up and down during this period. 2014 seems even more peculiar than 2016 in that there were far fewer HRs that year than any other year that I looked at (never heard anyone claim that the ball was deadened that year, tho). The 2014 Runs total was the lowest, too, but not by nearly as much as HRs. The dramatic rise in HR and Runs in 2015 seems not so much a surge in offense as it was a return to the mean from the unusually low totals of 2014.
I thought that batted ball data might provide some possible answers. It stands to reason that higher hard contact rates, higher pull rates and higher fly ball rates might account for the HR surge. I looked at MLB batted ball data back to 2007. Hard contact % did rise in 2016 but so did soft contact as medium contact declined. There were even more dramatic rises in hard contact rate from 2009 to 2010 and from 2011 to 2012. HRs did rise dramatically from 2011 to 2012 but actually dropped dramatically from 2009 to 2010. Pull rate also rose in 2016 but actually was higher in 2014 when HRs were at a recent historic low. Pull rates havent seemed to vary much in this period, never changing by even as much as 1.5% year to year. Hard/Medium/Soft contact rates have bounced up and down. I'm not sure how much I trust the contact statistics because in 2011 hard contact rate was dramatically lower and soft contact was dramatically higher than any other year before returning to more normal levels the next year. The HRs and Runs that year were rather low but not nearly as low as 2014 which had normal hard and soft contact rates. Fly ball rates are down somewhat in the last 5 years and line drive rates are up some during this time. The 2016 FB rate was up a bit but both the FB and LD rates were virtually the same as the historically low HR year of 2014.
My conclusion from this is that the 2016 HR rate is probably mostly random variation, w possibly some help from the increase in hard contact. I would expect that it will regress to a more normal figure for the pitch/Fx era, which is an average of 4834, which is very close to the 2015 total.
A few other interesting items: Strikeouts have increased every year since 2005. Walks have gone up and down and then up again the last 2 years, but are about the same now as they were in 2005. Runs have gone down every year since 2006 before increasing the last 2 years. Interestingly, the average age of MLB players has gone done or stayed the same since 2004, decreasing from 29.3 to 28.4 during that time. Perhaps this is because of careers being shortened by the discouraging of PED use brought about by testing.
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