MLB: How baseball has changed over the decade

DENVER, CO - AUGUST 05: The Colorado Rockies infield employ the infield shift as they defend against the Seattle Mariners during interleague play at Coors Field on August 5, 2015 in Denver, Colorado. The Rockies defeated the Mariners 7-5 in 11 innings. (Photo by Doug Pensinger/Getty Images)
DENVER, CO - AUGUST 05: The Colorado Rockies infield employ the infield shift as they defend against the Seattle Mariners during interleague play at Coors Field on August 5, 2015 in Denver, Colorado. The Rockies defeated the Mariners 7-5 in 11 innings. (Photo by Doug Pensinger/Getty Images) /
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(Photo by Dilip Vishwanat/Getty Images)
(Photo by Dilip Vishwanat/Getty Images) /

The long ball

Obviously, MLB teams emphasize the long ball more today than ever in history…but how much greater that emphasis is may still be surprising.

In 2019, MLB teams averaged 226 home runs, a full 34 percent increase from the 168 those same teams averaged during the final season of the century’s first decade.

That 34 percent increase has hardly been a gradual or incremental one. As recently as 2014, the average number of home runs per team had actually fallen, to 140.

Since 2014, however, changes in the approaches teams take to generating offense – most of them empowered by the increasing role the study of physics has played in coaching – have delivered a boost to power that is almost logarithmic.

The table below, which shows the change in home runs per team per season, illustrates this. acceleration.
Season      HR/team      Change
2009              168
2010              154              -9.4%
2011              152              -1.3%
2012              164                7.9%
2013              155              -5.5%
2014              140              -9.7%
2015              164              17.1%
2016              187              14.0%
2017              204                9.1%
2018              186              -8.9%
2019              226              21.5%

The impact of this change shows up dramatically in individual home run performance. In 2009, 87 major league players – just short of three per team – reached the 20 home run threshold. By the 1014 season, that number had actually dropped to just 57 – fewer than two per team.

Yet during the 2019 season, 130 players – more than four per team and more than twice as many as five years earlier – reached the 20 home run plateau.

The home run increase has driven a concurrent increase in run production that defies a decline in batting average. In 2009, the MLB batting average was .262, and teams produced 4.61 runs per game. In 2019, averages fell to .252, but runs per game rose nearly five percent to 4.83. Hitters had become efficiency experts.