Single Season Leaders for Isolated Power in the American League

Isolated Power is a SABERmetric statistic that attempts to describe a hitter's overall effectiveness by measuring his ability to generate extra base hits. Isolated Power was created by baseball great Branch Rickey along with Allan Roth during the 1950's and they termed it Power Average. Isolated Power is calculated by substracting batting average from slugging percentage.

Important notes: One-hundred single season games played are needed to make this list, raw averages are presented to further clarify the one-hundred greatest single season American League isolated power averages of all-time, and a bold faced entry denotes that the player was active during the previous season.
"The fans began pouring into the ballparks across the country to see the 'Babe' (Ruth) in action. Baseball was again the country's national pastime, bringing back the fans who had soured on the sport by the Black Sox scandal in 1919." - BaseballHistorian.com (Babe Ruth, The Power Days)
Isolated Power
Single Season American League Leaders

'Top 100'
Babe Ruth .472 (.47162) 1920 New York Yankees AL 1
Babe Ruth .469 (.46852) 1921 New York Yankees AL 2
Mark McGwire .418 (.41844) 1996 Oakland Athletics AL 3
Babe Ruth .417 (.41667) 1927 New York Yankees AL 4
Mark McGwire .410 (.41009) 1995 Oakland Athletics AL 5
Lou Gehrig .392 (.39212) 1927 New York Yankees AL 6
Babe Ruth .386 (.38619) 1928 New York Yankees AL 7
Jimmie Foxx .385 (.38462) 1932 Philadelphia Athletics AL 8
Frank Thomas .376 (.37594) 1994 Chicago White Sox AL 9
Albert Belle .374 (.37363) 1995 Cleveland Indians AL 10
Jim Thome .373 (.37292) 2002 Cleveland Indians AL 11
Babe Ruth .373 (.37259) 1930 New York Yankees AL 12
Babe Ruth .372 (.37165) 1923 New York Yankees AL 13
Mickey Mantle .370 (.36965) 1961 New York Yankees AL 14
Hank Greenberg .369 (.36871) 1938 Detroit Tigers AL 15
Babe Ruth .366 (.36566) 1926 New York Yankees AL 16
Babe Ruth .361 (.36106) 1924 New York Yankees AL 17
Babe Ruth .357 (.35714) 1922 New York Yankees AL 18
Albert Belle .357 (.35680) 1994 Cleveland Indians AL 19
Jimmie Foxx .356 (.35575) 1938 Boston Red Sox AL 20
Mickey Mantle .353 (.35272) 1956 New York Yankees AL 21
Babe Ruth .353 (.35271) 1929 New York Yankees AL 22
Ken Griffey, Jr. .351 (.35104) 1994 Seattle Mariners AL 23
Roger Maris .351 (.35085) 1961 New York Yankees AL 24
Travis Hafner .350 (.35022) 2006 Cleveland Indians AL 25
David Ortiz .349 (.34946) 2006 Boston Red Sox AL 26
Jimmie Foxx .347 (.34729) 1933 Philadelphia Athletics AL 27
Manny Ramirez .346 (.34624) 2000 Cleveland Indians AL 28
Carlos Pena .345 (.34490) 2007 Tampa Bay Devil Rays AL 29
Mark McGwire .344 (.34426) 1997 Oakland Athletics AL 30
Rudy York .344 (.34400) 1937 Detroit Tigers AL 31
Lou Gehrig .344 (.34370) 1934 New York Yankees AL 32
Jim Gentile .344 (.34362) 1961 Baltimore Orioles AL 33
Ted Williams .343 (.34286) 1957 Boston Red Sox AL 34
Lou Gehrig .343 (.34251) 1930 New York Yankees AL 35
Ken Griffey, Jr. .342 (.34211) 1997 Seattle Mariners AL 36
Lou Gehrig .342 (.34197) 1936 New York Yankees AL 37
Brady Anderson .340 (.34024) 1996 Baltimore Orioles AL 38
Babe Ruth .336 (.33565) 1919 Boston Red Sox AL 39
Jimmie Foxx .334 (.33405) 1939 Boston Red Sox AL 40
Reggie Jackson .333 (.33333) 1969 Oakland Athletics AL 41
Jim Thome .333 (.33270) 2001 Cleveland Indians AL 42
Hank Greenberg .332 (.33165) 1937 Detroit Tigers AL 43
Alex Rodriguez .331 (.33105) 2007 New York Yankees AL 44
Hank Greenberg .330 (.32984) 1940 Detroit Tigers AL 45
Manny Ramirez .330 (.32950) 1999 Cleveland Indians AL 46
Ted Williams .329 (.32903) 1960 Boston Red Sox AL 47
Juan Gonzalez .329 (.32902) 1996 Texas Rangers AL 48
Ted Williams .329 (.32895) 1941 Boston Red Sox AL 49
Mark McGwire .329 (.32855) 1987 Oakland Athletics AL 50
Babe Ruth .328 (.32772) 1931 New York Yankees AL 51
Ken Griffey, Jr. .327 (.32701) 1998 Seattle Mariners AL 52
Hank Greenberg .327 (.32696) 1946 Detroit Tigers AL 53
Joe DiMaggio .327 (.32689) 1937 New York Yankees AL 54
Albert Belle .327 (.32677) 1998 Chicago White Sox AL 55
Al Simmons .327 (.32671) 1930 Philadelphia Athletics AL 56
Ted Williams .325 (.32490) 1946 Boston Red Sox AL 57
Ken Griffey, Jr. .325 (.32477) 1996 Seattle Mariners AL 58
Alex Rodriguez .324 (.32372) 2002 Texas Rangers AL 59
Juan Gonzalez .323 (.32276) 1993 Texas Rangers AL 60
Lou Gehrig .321 (.32149) 1931 New York Yankees AL 61
Frank Robinson .321 (.32118) 1966 Baltimore Orioles AL 62
Carlos Delgado .320 (.31986) 2000 Toronto Blue Jays AL 63
Troy Glaus .320 (.31972) 2000 Anaheim Angels AL 64
Babe Ruth .319 (.31947) 1932 New York Yankees AL 65
Jimmie Foxx .319 (.31911) 1934 Philadelphia Athletics AL 66
Harmon Killebrew .318 (.31793) 1961 Minnesota Twins AL 67
Jason Giambi .317 (.31731) 2001 Oakland Athletics AL 68
Bob Hamelin .317 (.31731) 1994 Kansas City Royals AL  
Rocky Colavito .317 (.31697) 1958 Cleveland Indians AL 70
Mark McGwire .317 (.31692) 1992 Oakland Athletics AL 71
Boog Powell .316 (.31604) 1964 Baltimore Orioles AL 72
Cecil Fielder .314 (.31414) 1990 Detroit Tigers AL 73
Jason Giambi .314 (.31373) 2000 Oakland Athletics AL 74
Albert Belle .312 (.31229) 1996 Cleveland Indians AL 75
Juan Gonzalez .312 (.31188) 1998 Texas Rangers AL 76
Jim Thome .310 (.31020) 2006 Chicago White Sox AL 77
Don Mincher .310 (.31010) 1964 Minnesota Twins AL 78
Hank Greenberg .310 (.31000) 1939 Detroit Tigers AL 79
Harmon Killebrew .308 (.30811) 1969 Minnesota Twins AL 80
Ken Griffey, Jr. .308 (.30756) 1993 Seattle Mariners AL 81
Ted Williams .307 (.30742) 1949 Boston Red Sox AL 82
Rafael Palmeiro .306 (.30619) 1999 Texas Rangers AL 83
Jermaine Dye .306 (.30612) 2006 Chicago White Sox AL 84
Mickey Mantle .306 (.30561) 1955 New York Yankees AL 85
Jim Spencer .305 (.30508) 1979 New York Yankees AL 86
Jason Giambi .305 (.30493) 2006 New York Yankees AL 87
Manny Ramirez .305 (.30473) 1998 Cleveland Indians AL 88
Manny Ramirez .305 (.30458) 2004 Boston Red Sox AL 89
David Ortiz .304 (.30449) 2005 Boston Red Sox AL 90
Jay Buhner .304 (.30426) 1995 Seattle Mariners AL 91
Alex Rodriguez .304 (.30380) 2001 Texas Rangers AL 92
David Ortiz .304 (.30357) 2003 Boston Red Sox AL 93
Fred Lynn .303 (.30320) 1979 Boston Red Sox AL 94
Harmon Killebrew .303 (.30254) 1962 Minnesota Twins AL 95
Jimmie Foxx .302 (.30249) 1930 Philadelphia Athletics AL 96
Manny Ramirez .302 (.30246) 2001 Boston Red Sox AL 97
David Ortiz .302 (.30241) 2004 Boston Red Sox AL 98
Alex Rodriguez .301 (.30148) 2003 Texas Rangers AL 99
Manny Ramirez .301 (.30144) 2005 Boston Red Sox AL 100
Current Through End of 2007 Regular Season


Did you know this stat was originally called Power Average? Did you know it had been around for the past fifty (50) years? Should Isolated Power be more commonly used & quoted by the media? Join in our advanced baseball stats forum on Baseball Fever?

The code to write the single season isolated power league splits was developed in 2005, launched during 2006 and made possible by your support — please continue helping us create these kinds of pages by supporting our site.

The National League single season record for isolated power was set in 2001 by Barry Bonds of the San Francisco Giants. The American League single season record for isolated power is on this page. Is either the Career Leader for Isolated Power?
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