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Obvious dividing line from MLB stats of 1968 to stats of 1969

Cubs slugger Sammy Sosdid not receive enough votes for inductiinBaseball's Hall Fame. | Getty Images

Cubs slugger Sammy Sosa did not receive enough votes for induction into Baseball's Hall of Fame. | Getty Images

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Not all baseball
statistics from all eras are created equal. Numbers from the pre-1920 dead-ball era can’t be judged on the same scale as those that followed. Home-run totals today are affected by conditions that have changed since Barry Bonds, Mark McGwire and Sammy Sosa were slammin’ ’em.

In comparing players across eras, sabermetricians have to be aware of the changing conditions. A run created in a low-scoring era is a bigger step toward winning than a run created in a time of high offense.

We don’t have to go all the way back to the dead-ball era for a demonstration. The 1960s were another time of rapidly changing conditions. And Cubs Hall of Famer Billy Williams was a powerful model of changing times.

The period of 1963-68 was as tough as it got for hitters at any time since the dead-ball era. One big factor was the redefinition of the strike zone in 1963. It was extended to the top of the shoulder to the knee, instead of the old armpits to the top of the knee.

Offense declined, and it all came crashing down in 1968. That was the season of Bob Gibson’s 1.12 ERA. Carl Yastrzemski led the American League with a .301 batting average, and there were only six qualifiers in the majors to break .300. Teams averaged only 3.41 runs per game in the AL, 3.43 in the National League.

That couldn’t be allowed to continue. Fans like offense. For 1969, the strike zone returned to its old armpits-to-the-top-of-the-knee definition and the mound was lowered from 15 inches to 10. Runs per game jumped 18 percent in the NL (to 4.05 per game) and 20 percent in the AL (to 4.09).

Which brings us to Williams. In 1968, he had a batting average/on-base percentage/slugging percentage line of .288/.336/.500. The next season, it was .293/.355/.474.

An OPS of .836 followed by one of .829 suggests remarkable consistency. But in 1968, the Cubs and their opponents averaged 7.5 runs per game. In 1969, that rose to 8.16. It took more runs to win a game in ’69 than in ’68.

That’s reflected in sabermetric numbers. OPS-plus normalizes to league average while adjusting for ballpark. An average hitter has an OPS-plus of 100. Williams was a great hitter (142 OPS-plus) in ’68 and merely very good (119) in ’69. Wins Above Replacement tells the same story, with a 4.8 offensive WAR in ’68 and a 3.2 oWAR the next season.

The raw numbers look similar, but taken in the context of their times, Williams’ production in ’68 translates into bigger steps toward winning.

There’s a bright line between ’68 and ’69 because of the rules changes, but baseball conditions are changing constantly. Advanced metrics help us cut through the differences and compare players on the basis of how much their contributions meant in terms of winning ballgames.



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