As you’re probably aware, more home runs were hit during the 2017 season than in any prior year. A lot more, actually, as the 2017 total of 6105 round-trippers was a whopping 415 more than the previous record season in 2000.

More after the jump on the season of the long ball.

As shown below, the seventeen year gap between record home run seasons is the second longest of the modern era, so it should not be a surprise that a new record has been set.

What is more surprising is the suddenness of the change to the higher long ball totals, coming on the heels of the longest down trend of the modern era, as shown below.

Looking at year-over-year changes in home run totals, this is the third straight year of increases, something that’s happened only twice before in the post-war period (the other two times, in 1985-87 and 1998-2000, also culminated in new record seasons).

Looking at the 3-year trend, the more than 40% jump since 2014 in the largest of the post-war period.

Nearly every hitter now has at least a little pop, as show below for home runs by batting order position. The “heart” of the batting order in positions 3-6 now account for less than 60% of home runs, while the top and bottom each account for more than 20%.

In terms of numbers of players at different home runs levels, those hitting ten or more home runs has expanded from almost none in the dead ball era to nearly 8 per team today, while those compiling 200+ PA and hitting no home runs at all have virtually disappeared (last year marked the first time with fewer than 5 such major league players for three straight seasons).

Looking at the same data on a line chart shows the 1-9 home run group at its lowest level since World War II while the 10+ and 20+ groups are at record highs, and the 30+ group nearly so.

Looking at in game home run trends, here are a couple that caught my eye. The first line on the chart below shows percent of home runs hit with a batter platoon advantage, increasing steadily through the early 1980s, then declining until the mid-1990s, and mostly steady since then. The rise can be attributed to the growth in switch hitters and to greater use of pinch-hitters (the latter peaking from 1958-62 at 2.96% of home runs, and with no 5-year period since 1983-87 above 2.5%). The decline phase from the early 1980s through the mid-1990s coincides with modern reliever usage and managers increasingly using relief pitchers to counter batter platoon advantages. The steady state since the mid-1990s reflects further refinements in reliever usage with 7th, 8th and 9th inning specialists, regardless of platoon advantage or disadvantage; the most recent period has also seen larger bullpens and shorter benches, giving managers fewer pinch-hitting options.

The second trend in the above chart is the increase in home runs with 0 outs, reflecting both a greater number of players with home run clout and a change in batting approach from trying to get on base to trying to do some damage. Illustrative of this change in batting approach is the percent of PA with zero out and the bases empty (occurring at the beginning of each half inning and following home runs with zero outs), with the 5 highest marks since 1950 all occurring in the past 5 seasons.

Home runs by inning are shown in the chart below. Relief specialization by inning has indeed reduced the frequency of late inning home runs. Of course, a decrease in late inning home runs means an increase somewhere else, in this case in the early innings, a trend also indirectly related to greater dependence on relief pitching; the dotted line showing a marked and steady decline in short starts indicates that managers today are far more likely to stick with an ineffective starter in the early innings, mainly because of the need to get a least a few innings from that starter to avoid overtaxing the bullpen.
The charts below show color coded team home run totals by season. The pre-expansion period shows a general rise in home run totals through the period for all teams, with the Yankees in the vanguard of that trend in the AL, and the Giants and the Phillies in the NL. Some of those season home run totals in the early years are especially low, led by the White Sox who failed to reach triple digits over a full decade (99 total home runs from 1902-11).

The influence of ballparks on home run production has always been a significant factor and remains so today. Sudden changes in team results often coincide with moves to new ballparks.

Looking at home run rankings, again color coded by team and season, provides the results below. The longest runs leading the majors in home runs are the 7 seasons (1949-55) by the Dodgers and 6 years (1936-41) by the Yankees. Expansion era dominance is less pronounced, given more teams and greater player movement between them. Thus, the longest expansion era run leading the pack is only three years by the Braves (1965-67), Tigers (1990-92), Mariners (1997-99) and Rangers (2001-03).