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Chris Davis and Normalized Home Run Rates

Chris Davis hit his 51st home run of the season last night. 20 years ago, that would have been a pretty big deal, but the years around the turn of the century reset the bar for newsworthy home run totals. After having only two 60 homer seasons in the first 100+ years of baseball, we saw six such seasons in four years. 50 homer seasons used to be the stepping stone to greatness; now, Davis is still 22 home runs away from the single season record.

As we know, though, the game as its being played today doesn’t look like the game that was being played 15 years ago. The strike zone is bigger, the players are smaller, and both runs and home runs are much harder to come by these days. Chris Davis might not set any real records, but hitting 51 home runs (and counting) in this offensive context is still an accomplishment worth celebrating.

But rather than just leave it at that, we can actually just look at Davis’ home run rate relative to 2013 norms, and then compare that to other 50 HR seasons to see how Davis’ HR rate stacks up throughout recent history. So let’s do just that. In the following table, you’ll see each player who has hit 50 home runs in the 50 years preceding this one, with Davis’ 2013 season inserted into the mix, giving us 28 different 50 HR seasons to look at. I’ve also listed the ratio of plate appearances to home runs, the league average PA/HR ratio for that season, and then an index metric I’ve called HR+, that is simply a player’s PA/HR ratio divided by the league PA/HR ratio. Think of it as wRC+, just without the park adjustments, and for dingers only.

Season Name PA HR PA/HR LgHR HR+
1998 Mark McGwire 681 70 9.7 37.2 382
2001 Barry Bonds 664 73 9.1 34.2 376
1965 Willie Mays 638 52 12.3 45.7 372
1990 Cecil Fielder 673 51 13.2 48.3 366
1998 Sammy Sosa 722 66 10.9 37.2 339
1996 Mark McGwire 548 52 10.5 35.7 338
1999 Mark McGwire 661 65 10.2 34.3 337
1977 George Foster 689 52 13.3 44.3 334
1997 Mark McGwire 657 58 11.3 37.8 334
2013 Chris Davis 625 51 12.3 39.4 321
2010 Jose Bautista 683 54 12.6 40.2 318
2002 Jim Thome 613 52 11.8 36.9 312
2001 Sammy Sosa 711 64 11.1 34.2 308
1995 Albert Belle 631 50 12.6 38.4 304
1999 Sammy Sosa 712 63 11.3 34.3 303
1997 Ken Griffey Jr 704 56 12.6 37.8 300
2007 Alex Rodriguez 708 54 13.1 38.1 290
2002 Alex Rodriguez 725 57 12.7 36.9 290
1998 Ken Griffey Jr 720 56 12.9 37.2 289
2006 Ryan Howard 704 58 12.1 34.9 287
2005 Andruw Jones 672 51 13.2 37.1 281
1998 Greg Vaughn 661 50 13.2 37.2 281
2007 Prince Fielder 681 50 13.6 38.1 279
2006 David Ortiz 686 54 12.7 34.9 274
2001 Luis Gonzalez 728 57 12.8 34.2 268
1996 Brady Anderson 687 50 13.7 35.7 259
2001 Alex Rodriguez 732 52 14.1 34.2 243
2000 Sammy Sosa 705 50 14.1 33.4 237

Not surprisingly, we see Bonds and McGwire at the top, but interestingly, look at how close Willie Mays was in 1965 to Bonds’ record 2001 season. While Bonds ended up with 21 home runs, a large part of that difference was just the league norms at the times in which they played. In fact, even Cecil Fielder‘s somewhat forgotten 51 homer season in 1990 was not very far off the mark of Bonds’ HR rate once you adjust for league averages in that season.

And look where Davis stands. There’s four Mark McGwire seasons ahead of him, plus the Bonds/Mays/Fielder group, plus George Foster‘s 1977 season, but Davis’ 2013 season stands ninth in normalized home run rate, well ahead of seasons with bigger HR totals. There’s no trophy for top 10 HR rate relative to league average over an arbitrary timeframe, but this is still an accomplishment worth noting.

But, while the last 50 years is a convenient timeframe for our leader boards, since they can display up to 50 seasons at one time, this window annoying excludes some of the more famous HR seasons in history. So, let’s see how the players in the previous 50 years to our sample did, giving us a range of 1914 to 1963. Prepare to laugh, or be amazed, or both.

Season Name PA HR PA/HR LgHR HR+
1920 Babe Ruth 615 54 11.4 150.1 1,318
1927 Babe Ruth 691 60 11.5 103.6 899
1921 Babe Ruth 693 59 11.7 101.9 867
1928 Babe Ruth 684 54 12.7 87.4 690
1932 Jimmie Foxx 701 58 12.1 71.1 588
1938 Hank Greenberg 681 58 11.7 64.6 550
1930 Hack Wilson 709 56 12.7 62.1 490
1938 Jimmie Foxx 685 50 13.7 64.6 471
1947 Johnny Mize 664 51 13.0 60.9 467
1947 Ralph Kiner 666 51 13.1 60.9 466
1949 Ralph Kiner 667 54 12.4 56.4 456
1961 Roger Maris 698 61 11.4 40.1 350
1961 Mickey Mantle 646 54 12.0 40.1 335
1956 Mickey Mantle 652 52 12.5 41.5 330
1955 Willie Mays 670 51 13.1 42.7 325

Babe Ruth only hit 50 home runs in a season four times, but three of the four times he did it, the league average PA/HR rate was over 100, meaning that an average player in those years would hit five to seven home runs per year. In 1920, when Ruth hit 54 home runs, that accounted for 8.5% of the entire league’s total. These numbers just destroy what we’ve seen in the last 50 years, because the game was entirely different back then, with only a few players hitting balls out of the ballpark on a regular basis. The home run giants of that era towered over their competition in a way that no one does anymore.

Interestingly, look at where Maris’ HR+ rate lies in comparison to Cecil Fielder‘s 1990 season. While there will always be some who attempt to proclaim Maris the “true HR champ”, since they prefer to invalidate all accomplishments during the “Steroids Era”, that argument is already along the path of adjusting for seasonal context. If we’re going to start down that path, might as well go all the way and acknowledge that Fielder’s 51 HR season was more impressive, given the difference in league average HR rates between 1961 and 1990. But, then, neither Fielder nor Maris can stack up to Ruth’s ridiculous accomplishments, given the norms of his day.

True home run champ? I’ll go with Barry Bonds, chemicals and all, given that he hit more home runs in a season than anyone else ever, and that’s really the answer to the question most people want to know. Most impressive HR hitter, relative to his own time? That’s Ruth, and it will be Ruth forever, barring some kind of weird changes to the rules involving pitchers throwing multiple balls at the hitter simultaneously.

Chris Davis isn’t in either of those conversations. And even with a huge barrage to end the year, he’s not going to end up in them. But, he’s playing in different environment than the one we saw 15 years ago, and what he’s accomplished is pretty remarkable. So kudos to Davis on his 51 homer (and counting) season, a feat that stands up pretty well against most of history’s best HR seasons.