scoring 40% more runs and hitting four times as many home runs as they had in 1918. Baseball historians debate the abruptness of this change, with no consensus on its cause. Six popular theories have been advanced: Changes in the ball: This theory claims that owners replaced the ball with a newer, livelier ball (sometimes referred to as the "jackrabbit" ball), presumably with the intention of boosting offense and, by extension, ticket sales. The theory has been rebutted by Major League Baseball. The yarn used to wrap the core of the ball was changed prior to the 1920 season, although testing by the United States Bureau of Standards found no difference in the physical properties of the two different types of balls. The so-called "livelier" ball was actually introduced in 1911, when the league began using a cork-centered ball, as opposed to rubber, and that year the number of total home runs was 514, having been 361 the previous season. Frank Schulte became the first player of the 20th century to reach twenty home runs in a season. Outlawing certain pitches: Pitches now considered illegal, per MLB Rule 6.02(c), were outlawed. This included the shine ball, emery ball, and spitball (a very effective pitch throughout the dead-ball era). This theory states that without such effective pitches in the pitcher's arsenal, batters gained an advantage. When the spitball was outlawed in 1920, MLB recognized seventeen pitchers who had built their careers specializing in the spitball and permitted them to continue using it; the last pitcher allowed to do so, Burleigh Grimes, pitched until the end of 1934. More baseballs per game: The fatal beaning of Cleveland Indians shortstop Ray Chapman in August 1920 led to a rule that the baseball must be replaced every time that it got dirty. With a clean ball in play at all times, players no longer had to contend with a ball that "traveled through the air erratically, tended to soften in the later innings, and as it came over the plate, was very hard to see." Stat keeping and rule changes: In 1920, the major leagues adopted writer Fred Lieb's proposal that a game-winning home run with men on base count as a home run, even if its run is not needed to win the game. Owners tried unsuccessfully to eliminate the intentional walk. They succeeded only in changing the rules to require that the