MLB home run projections are bonkers
In 2018, MLB released the results of an independent study conducted by a committee of scientists "on the causes of the increased home run rate in the game since 2015." The panel found the surge in home run hitting over that span was due, at least in part, "to a change in the aerodynamic properties of the baseball." More specifically, the experts found the ball used in games over the past few years created less drag as it moved through the air, causing it to travel further. It appears to remain a problem.
The Washington Nationals hit back-to-back-to-back-to-back home runs against the San Diego Padres in June, becoming the first team in MLB history to hit four consecutive home runs on more than one occasion. A few days later the Arizona Diamondbacks and Philadelphia Phillies put on an impromptu home run derby, smashing a record 13 home runs combined in one game. Christian Yelich (Milwaukee Brewers), Cody Bellinger (Los Angeles Dodgers) and Pete Alonso (New York Mets) are each threatening Barry Bonds' season home run record and Todd Frazier of the Mets hit a 373-foot home run against the San Francisco Giants practically using just one arm and one leg.
Heading into the all-star break, there have been 3,691 home runs hit in 2019, a historically high rate of 1.37 per game, which means we can expect the current home run record, set in 2017 (6,105), to be obliterated by year's end.
A whopping 46 players are projected to hit 30 or more home runs this season, per Dan Szymborski's projections, one fewer than there was in 2000, a major league record. But there are eight others who are tabbed for 29 home runs this year, so that record is also in jeopardy. Eight players are projected to hit 40 or more home runs in 2019 with Yelich and Bellinger leading all hitters with 47 by season's end. And those estimates are likely conservative. For example, Yelich, Bellinger and Alonso are only penciled in to hit 16, 17 and 15 more home runs, respectively, this season, according to Szymborski's projections - a low number considering all have 30 or more home runs before the all-star break.
Despite that conservatism, team home run records are poised to fall.
The 2018 New York Yankees set the record for most home runs in a season with 267. According to Szymborski's projections they are expected to hit a whopping 322 in 2019. The Minnesota Twins are expected to match the 2018 mark with 287 home runs hit this year. The Brewers (269), Philadelphia Phillies (265) and San Diego Padres (260) could join them, too.
Based on everything we have seen during the first half of the season - how many home runs were hit, by which team, etc. - we can simulate the season thousands of times and come up with a range of totals for a year-end number. Using this, we can expect major league teams to hit at least 6,463 home runs by the end of the regular season - that would break the record set in 2017 (6,105) by almost 400 home runs. In these simulations we even see a high-water mark of 6,873 home runs hit this season. For perspective, that would be the single biggest jump in the record since it was broken by 645 home runs in 1987.