Best MLB Hitting Seasons of All Time Adjusted for Competitive Balance

Who is the best hitter in baseball history? This is the classic baseball question. We have tools like fWAR to help us answer these questions today. However, we have a problem: levels of competition have never been uniform. If you search for the best single-season fWARs of all time, you get a lot of players in the live ball era, a few players in the 50s, and Barry Bonds. I don't know about you, but I'm skeptical that the best seasons in baseball history were all played in the 20s or were Barry Bonds:

SeasonNameRaw fWAR
1923Babe Ruth15
1921Babe Ruth13.9
1920Babe Ruth13.3
1927Babe Ruth13
2002Barry Bonds12.7
2001Barry Bonds12.5
1924Babe Ruth12.5
1924Rogers Hornsby12.5
1927Lou Gehrig12.5
1926Babe Ruth12
2004Barry Bonds11.9
1946Ted Williams11.8
1942Ted Williams11.6
1956Mickey Mantle11.5
1917Ty Cobb11.5
1957Mickey Mantle11.4
1932Jimmie Foxx11.3
1921Rogers Hornsby11.2
1967Carl Yastrzemski11.1
1929Rogers Hornsby11.1


Levels of competition have varied over time. We all know that Babe Ruth didn't have to hit against Satchel Paige, and so was able to face weaker competition than players post-integration. As levels of competition go down, better players are able to stand out more. Athletic training, steroids, spitballs, and international recruitment have varied over the years.

I want to adjust single-season performance for competitiveness. We'll never adjust for things like physical fitness (could Babe Ruth hit at an Aroldis Chapman fastball?), but we can adjust for the general distribution of competitiveness by season. I downloaded all qualified players' fWAR from Fangraphs since 1910. I then calculated the standard deviation of fWAR by season. A higher standard deviation indicates that there is more variation between the average player and the best or worst players on the extremes. Here's what it looks like:

You can see that baseball has grown more competitive over time. The best and worse players stood out less in 2010 than in 1930. You can see a good-sized spike during the steroids era, where players like Barry Bonds presumably benefitted disproportionately from performance enhancing drugs. That bump goes away after drug testing begins.

We can also weight individual seasons by competitiveness and by games played (152 vs 162). Here are the best seasons of all time by weighted fWAR*:

SeasonNameWeighted fWAR
1962Willie Mays13.7
1926Babe Ruth13.6
1915Ty Cobb13.5
2004Barry Bonds13.0
1915Eddie Collins12.8
1981Mike Schmidt12.8
1991Cal Ripken12.6
1987Wade Boggs12.6
1911Ty Cobb12.5
2013Mike Trout12.4
1968Carl Yastrzemski12.3
1994Jeff Bagwell12.3
1913Eddie Collins12.2
1914Benny Kauff12.2
1919Babe Ruth12.2
1947Ted Williams12.1
1925Rogers Hornsby12.1
2005Alex Rodriguez12.1
1985Rickey Henderson12.0
2012Mike Trout12.0

* Please note that the weights are not directly comparable to normal fWAR.

Not bad! The all-time greats from the 1920s are represented, but so are modern players. Mike Trout already has two of the best single seasons of all time. Alex Rodriguez, Rickey Henderson, Barry Bonds, Cal Ripken and Jeff Bagwell all show up. In fact, the single-season distribution is pretty even overall. 

Let's get out of single seasons. Who were the best players of all time by weighted fWAR?

NameCareer Weighted fWAR
Barry Bonds158.5798
Willie Mays142.6258
Hank Aaron130.8907
Tris Speaker127.6107
Mike Schmidt126.5993
Ty Cobb119.9339
Rickey Henderson113.6577
Alex Rodriguez113.5173
Babe Ruth113.2207
Eddie Collins108.5147
Stan Musial108.1189
Rogers Hornsby106.2226
Cal Ripken104.8136
Joe Morgan104.0492
Carl Yastrzemski102.6251
Albert Pujols101.6452
Frank Robinson101.1763
Ted Williams99.46524
Wade Boggs98.96848
George Brett98.11801

Players like Lou Gehrig (#10 in unweighted fWAR, out of the top-20 weighted) take a big hit. The 1920s and 1930s were a time of huge outlying performances. Players from the 70s and 80s get a big boost, pushing Henderson, Schmidt, Ripken, and others up. Pujols stands out as a mostly post-steroids era performer. 

What do you all think? Does this change the way we should consider players from the Golden Age?