RULE 1.09:

The ball shall be a sphere formed by yarn wound around a small core of cork, rubber, or similar material, covered with two strips of white horsehide or cowhide, tightly stitched together. It shall weigh not less than five nor more than 5¼ ounces avoirdupois and measure not less than nine nor more than 9¼ inches in circumference.

The cover of the May 1955 issue of Baseball Digest had a headline that seems more appropriated for a modern supermarket tabloid than for a baseball magazine.

“Contents of the Suppressed Report! Flaws in Ball Exposed!”

University of Wisconsin professors Arthur Mansfield and Robert Francis conducted a two-year study of major league baseballs. Their findings were disturbing, which resulted in heavy pressure being brought on the researchers by the baseball manufacturers.

Unlike today, when one company, Rawlings , produces all the baseballs used in major league games, five firms produced major league baseballs during the 1950s.

The research revealed that:

1. Forty-five percent of the baseballs measured either less than nine inches or more than 9¼ inches in circumference.

2. Some baseball covers were half again as thick as others.

3. The rebound height of baseballs varied by as much as 16 percent.

4. The number of twists or yarn per inch varied by more than 25 percent.

Jim Gallagher, chairman of the Official Rules Committee, reacted:

“We fret over the accuracy of our records and then pay no attention to the accuracy of the main thing that goes into those records—the ball.”

Gallagher was right on target.

One Big Ten baseball coach said, “The difference is so great that against a certain (manufacturers) ball, I play my outfielders in 25 more feet than usual.”

Of the 56 baseballs tested from the five different manufacturers, 26 were too large and one was too small, but of greatest significance was the ball’s rebounding strength.

The rebound height of new baseballs varied from 18.82 inches to 22.14 inches when the ball was dropped 48 inches onto a marble slab.

The researchers concluded that there were variations in the thickness of the cover of baseballs, in the height of the seams, in the rebounding ability, and in the size and weight of different baseballs.

Even baseballs from the same manufacturer were different.

In 2010, offensive production had decreased greatly. The following table compares 2010 with 2009 and 2006.



2010 4.56 0.949 0.332 0.409 0.262
2009 4.82 1.128 0.336 0.428 0.267
2006 4.97 1.123 0.339 0.437 0.275


2010 4.38 0.905 0.327 0.401 0.257
2009 4.43 0.958 0.331 0.409 0.259
2006 4.76 1.097 0.334 0.427 0.265

What has caused the decrease? Are the pitchers getting better? Are the hitters getting worse? Has the strike zone changed? Is the defense better? Has the use of performance enhancing substances decreased?

All of the above questions are difficult, if not impossible to answer conclusively, but one variable that can be tested is the one that two researchers investigated almost 60 years ago. Compare the rebounding ability of today’s baseball with that of baseball’s from the not-too-distant past.


Allen, Phil. “Here’s What’s in the Report and Why It Was Suppressed.” Baseball Digest . May, 1955.

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