Craig Tomarkin / Baseball History

ERA ANALYSIS

By Craig Tomarkin

I identified critical changes in scoring patterns over time through baseball history. After I was done, I noticed that these changes strongly corresponded to dates major evolutionary changes in baseball. The numbers have been updated through the 2000 season.

This confirms that the 10 eras of baseball history defined by major rules changes correspond to changes scoring. Other subtle changes in the rules created sub-eras.

Era	Description	Year	Runs/G	Change	Index
1	National Register	1871	8.0		176
2	Pre Modern Rules - Est. NL	1876	5.6	-29.7%	124
3	Modern Rules	1893	6.0	7.5%	133
4	Dead Ball Era  - Est. AL	1901	3.9	-33.3%	86
5	Live Ball Era - Cork	1920	4.8	23.5%	107
6	War Years, Wide K Zone	1942	4.1	-16.0%	90
7	Golden Years - Integration	1947	4.5	9.4%	98
8	Growing Pains	1961	4.0	-10.0%	88
9	Designated Hitter	1973	4.3	6.4%	94
10	Free Movement, Exp II	1993-2000	4.9	14.9%	108
	Total		4.5		100

Remarks about the table:  

The period of 1901-1919 marked the span of vastly depressed run scoring, not 1903-1919 as some might expect due to implementation of the foul strike rule in the American League in 1903. Perhaps I should have called it something other than "Dead Ball - Est AL" so as not to confuse anyone's preconceived notion of the traditional reference to the "dead ball era" based on the 1903 rules change. Russell Wright, author of Dominating the Diamond, suggests calling it the Dirty Ball era, because the cause of lower scoring was not a dead ball per se (the live cork centered ball was introduced in 1910, not 1920) but rather the dirt and sweat that collected on the ball over the course of a game, which caused it to deaden its performance.

During the 1920 season, news balls were put into play to keep them from getting dirty, thus causing the live ball effect. Babe Ruth took advantage of these clean balls changing the game forever with the birth of the home run hitter. He drew such big crowds with his home runs that it was clear fans preferred home runs to pitching duels. Let the dead ball rest in peace.

In 1942, scoring took a sharp dive. In 1948 scoring returned. This era fits neatly around WWII.

Of keen interest is Era7, known by my nomenclature as the Golden Years. By integrating players from the Negro Leagues and players returning from World War II into Major League Baseball a statistical harmony (if not a racial harmony) was achieved that makes those years (index=98) the standard by which all "relative" adjustments are made. Perhaps, the ideal balance between strength of pitching and batting occurred from 1947 to 1960.

The most notable impact on runs scored is league expansion. Each time the league adds more players, the number of runs scored increases. Thus, indicating that pitching is always at a premium during an expansion. This is true, so much so in fact, that in 1961 when the American League expanded the Yankees belted out a whopping 240 homers, including Mantle's 54 and Maris' 61! A slew of sluggers from other AL teams also hit over 40 home runs. Why then is the scoring index for Era8 only 88?

Expansion adds new ballparks too. Some research has been done by others indicating that the impact of these new ballparks tends to boost scoring too.

Because the owners were concerned about increased scoring, in 1963 (the beginning of a sub-era) they agreed to widen the strike zone to the top of the armpit to the bottom of the knee. If you're still unsure that this change is enough to cause a newly expanded league to have decreased run production just look at the career stats of Sandy Koufax during the years of Era7 versus Era8. You'll be astounded!

To rejuvenate scoring in 1973 was the designated hitter was introduced.

1993 saw a big jump in scoring. But, it wasn't until 1994 that the MLB went to three divisions, so that was not the cause. It was more likely the addition of the Marlins and Rockies that caused the jump. I could have called it the "Juiced Ball Era" but, I called it "Free Movement, Exp II" because it seemed like the frantic free agency movement better described the period. Another possible reason for the dramatic increase in scoring is the widespread use of steriods among the players, but that is speculation.