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.