Eras of Play            Back to Reference Index

Diamond Mind Online® does not limit you to playing in the present. The rules, equipment, parks and other conditions under which baseball is played have constantly changed and evolved, with profound effects on tactics and performance, particularly the crucial balance between pitching and hitting. Diamond Mind Online® offers different “eras” in which leagues may be set. The choice of era affects the style of play and the performance of your players.

For example, Sandy Koufax turned in perhaps the most dominant five-year stretch of pitching in baseball history from 1962-66: 111-34, 33 shutouts, 1,444 strikeouts in 1,377 innings, ERA leader each season including three seasons under 2.00, and no-hitters four seasons in a row. But this performance was achieved in a pitcher-friendly home park during the Pitcher Era. It would be more difficult for him to achieve the same level of performance in the Home Run Derby Era, particularly in a hitters’ paradise home park like the new Citizens Bank Park in Philadelphia, nor would he be likely to complete games in the Home Run Derby Era at the rate that he did from 1962-66 (100 complete games in 176 starts). Conversely, it would be more difficult for Mark McGwire to replicate his HR performance from 1996-99 (52, 58, 70, 65) outside the Home Run Derby Era. In fact, most aspects of play are affected by the era in which a league is set.

The era in which a league is set determines the baseline rates for:

The era of play does not directly alter the likelihood that any particular tactic, such as a bunt or steal, will be employed, but rather, by altering the level and shape of offense generally, affects the decision-making process behind such tactics. So, for example, in an era that produces a lower-scoring environment, strategies that entail playing for a single run may tend to be used more frequently.

In addition to playing in the present (AL 2020 or NL 2020), Diamond Mind Online® offers seven historic eras of play: 

Dead Ball Era (1903-19)

The adoption of the foul strike rule in the NL in 1901 and the AL in 1903 ushered in the weakest offensive era in the history of baseball.  League averages dropped from around .280 to below .250 and strikeouts doubled.  Errors, although much more prevalent than today, were declining markedly as well, which also contributed to reducing scoring. 

There actually was a mini-surge in offense in 1911 with the introduction of the cork-centered ball, with average runs scored per game jumping in the AL from 3.6 to 4.6, Ty Cobb hitting .420 and Joe Jackson .408.  But pitchers quickly regained the upper hand with the proliferation of the emery ball, spit ball, shine ball and other "trick" pitches, driving runs scored per game back down to 3.7 in the AL in 1914.

So, what can you expect from the Dead Ball Era?  Lower batting averages, a lot less home runs, fewer strikeouts and walks, more complete games, and many more errors.

N.B. Diamond Mind Online® simulates the Dead Ball Era statistically, but cannot replicate the characteristics of play of the era, such as the prevalence of inside-the-park home runs.  The simulation may be distorted statistically if players and parks from out of the era are used.

Golden Age (1920-41)

The Dead Ball Era came to an abrupt end in 1919/20 as a result of the confluence of two factors: declining attendance and the fan appeal of the prodigious slugging of Babe Ruth.  There is some dispute about whether a “jackrabbit” actually was injected into the ball in 1919, when Ruth swatted a record 29 homers.  At least as important to the surge in offense were the practice of regularly introducing new balls into a game, which was adopted at this time, and the rule outlawing the “spitter” and other pitches involving defacement of the ball, which came into effect in 1920.  The major league batting average, which had remained around .250 from 1910-18, leaped to .268 in 1919 and over .280 in 1920, where it remained throughout the ensuing decade. 

The offensive pinnacle of the era occurred in 1930, when owners, in an attempt to boost attendance hurt by the Depression, "juiced" the ball, resulting in an NL league-wide batting average of .303.  For the rest of the decade, however,  the AL consistently outscored the NL by a wide margin.

What can you expect from the Golden Age?  The highest batting averages of any era of play offered; fewer errors than the Dead Ball Era, but more than subsequent eras.

Baby Boomers (1946-60)

The "Baby Boomers" Era was a time of beatniks, bomb shelters, and, in baseball, walks and home runs.  Bill James describes baseball in the '50s as "the most one-dimensional, uniform, predictable version of the game which has ever been offered to the public."

From 1920-39, NL teams averaged 2.79 walks per game (and over the entire Standard Era 3.12); from 1946-60, they averaged 3.41.  From 1920-39, they averaged 0.47 HR per game (and over the entire Standard Era 0.66); from 1946-60 they averaged 0.84.  However, the overall level of scoring between the Baby Boomers and Standard Eras was comparable (4.42 and 4.32 runs per game respectively), because of the comparative prevalence in the era of lumbering sluggers and the station-to-station style of play.

What can you expect from the Baby Boomers EraAs these numbers suggest, more home runs and walks, and fielding averages continuing to improve.

Pitcher Era (1963-68)

The “Pitcher Era” encompasses the seasons 1963-68 for both leagues. Expansion always produces an upward “blip” in offense and the AL in 1961 was no exception, with the league runs and HR per game increasing from 4.39 and 0.88 in 1960 to 4.53 and 0.95 in 1961. That upsurge, coupled with Roger Maris breaking Ruth’s single-season HR record, blinded owners to the fact that offense had, in fact, been in slow but steady decline for years. Instead they reacted by expanding the strike zone, ushering in the most pitching-dominated period in baseball since the Dead Ball Era.

The effect wasn’t immediately apparent. The drop in the numbers was modest in the AL in 1962 (runs/game to 4.44 and HR/game to 0.96), with a comparable drop in the NL to 4.48 and 0.89 (from 4.52 and 0.97, despite the fact that 1962 was an expansion year for the NL, which should have resulted in an increase in offense). But in 1963 the numbers dropped precipitously – to 4.08 and 0.92 in the AL and 3.81 and 0.75 in the NL.

This era culminated in 1968 – the “Year of the Pitcher” – in which the AL and NL runs and HR per game were a mind-boggling 3.41 and 0.68 and 3.43 and 0.55, respectively. Denny McLain won 31 games, Bob Gibson posted an ERA of just 1.12 with 13 shutouts, Don Drysdale threw 58.2 consecutive scoreless innings, and Carl Yastrzemski won the AL batting title with a record low mark of .301. The next season the strike zone was reduced to its former dimensions and the height of pitching mounds lowered, which (together with another round of expansion) restored a more reasonable balance between pitching and hitting.

What can you expect from a league in the Pitcher Era? Leagues will tend to have lower scores and league average ERA, lower batting averages and fewer home runs, among other impacts. In general, expect less offense and lower scoring games.

Turf Time (1969-92)

"Turf Time" is based on the NL seasons 1969-92 (to avoid the distorting effect of the DH in the AL).  Baseball entered a new era in 1969.  MLB's reaction to the "Year of the Pitcher" was to lower pitching mounds and reduce the strike zone to its former dimensions.  Offense in the AL was boosted further by the introduction of the designated hitter in 1973.  The year 1969 also was an expansion year, and with expansion from 10 to 12 teams in both leagues came divisional play and an expanded postseason. 

These factors combined to produce an immediate boost in offense.  In the NL, runs per game jumped from 3.43 to 4.05, HR from 0.55 to 0.76, and the league ERA from 2.99 to 3.60, and these figures remained around this level until the sudden surge of offense that ushered in the HR Derby Era in 1993.

The Turf Time Era also was notable for the proliferation of new "cookie cutter" symmetrical stadiums and artificial turf.  Houston was the first team to use "Astroturf" (in 1966) when grass refused to grow in the new Astrodome.  The White Sox, hoping for a boost in offense, were the second team to install it, in 1969.  Four more were added in 1970, with Riverfront and Three Rivers Stadiums opening and Busch Stadium and Candlestick Park converting.

The backlash, however, was swift.  No other existing stadiums converted to turf, and the White Sox became the first team to revert to grass in 1976, the Giants following suit in 1979.  The 10 new stadiums built between 1970 and 1990, (ending with the domed Tropicana Field) all had artificial turf; from 1990 and 2006, 18 new parks opened, all of which had natural grass.  There were still 10 turf parks in 1994; today there are just 2 (Toronto and Tampa Bay). 

What can you expect from a league in the Turf Time Era?  Despite the boost from the Pitcher Era, offense during Turf Time was comparatively weak, falling slightly below the overall level prevailing in the Standard Era.  You also will see the beginnings of a decline in pitch counts before fatigue begins to set in.

Home Run Derby Era (1993-2004)

The “Home Run Derby Era” is based on the National League seasons 1993-2004 (to avoid the distorting effect of the DH in the AL) The upsurge in home runs that began in 1993 was in full force by 1998, when Mark McGwire and Sammy Sosa both shattered the previous single-season home run mark, and culminated in Barry Bonds’s epic 73-HR season in 2001. In fact, half of all the 50-HR seasons in baseball history occurred between 1995 and 2002.

In 1992 the NL ERA was 3.51 and HR per game was 0.65. In 1993 the league ERA jumped to 4.05 and HR per game to 0.86. These figures jumped again in 1994 to 4.22 and 0.95, and remained around that level till another leap in 1999 to 4.57 and 1.12, with comparable numbers in 2000. Thereafter the numbers began to drop, but even so, league figures for 2004 were 4.31 and 1.10, until a more noticeable drop in 2005 (the first season in which a player with an initial positive test for banned steroids could be suspended) to 4.23 and 0.99.

So how will the Home Run Derby Era differ from previous eras? Obviously, there will likely be more home runs, and scores will be higher as offense rules the day. As one might expect, complete games will likely be fewer and earned run averages higher.

Moneyball Era (2005-2012)

The “Moneyball Era” is based on the National League seasons 2005-12 (to avoid the distorting effect of the DH in the AL). The drop in offense from 2004 to 2005 was reversed in 2006, with the NL ERA jumping back up from 4.23 to 4.49 and HR per game from 0.99 to 1.10.  However, since 2006 both have been in steady decline, falling each season to a low of 3.82 and 0.88, respectively, in 2011, before ticking up to 3.95 and 0.94 in 2012.

Two other noteworthy features of the era were increased strikeout and reduced walk rates, from 3.37 walks and 6.66 strikeouts per game in 2006 to 3.05 and 7.61 respectively in 2012.

So how will the Moneyball Era differ from previous eras?  Though less than the HR Derby Era, there still will be relatively more home runs.  There will be more strikeouts than in any other historical era.  And pitcher endurance drops even further from the HR Derby Era. 

AL 2021 and NL 2021

Diamond Mind Online®  offers as "eras" of play the most recently completed AL and NL seasons. Player performance in these eras of play is normalized on the basis of the league averages for those seasons, which have been trending towards more home runs, more strikeouts and lower batting averages.  In 2021, home runs and strikeouts again were at near or record levels in both leagues, with batting averages the lowest in decades.

So how will the AL and NL 2021 "eras" of play differ from previous eras?  Home runs will be hit at a rate exceeding the HR Derby Era, while batting averages will be comparable to the Pitcher Era; there will be more strikeouts than ever; and pitchers will tire more quickly than in any other era of play.

 Standard Era (1920-1992)

The “Standard Era” is, in effect, a neutral playing environment, in the modern, post-Dead Ball Era, based on an average of statistical performance in the NL from 1920-1992. This is the era of play for Classic standard leagues.

 

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