Baseball Toaster was unplugged on February 4, 2009.
After my look at rookie and veteran players, I was asked a few questions about the makeup of rookies over the years. So here goes.
I took a look at the average age for rookie throughout baseball history. Long story short, the numbers have held pretty steady at around 23-24 years. (I have the yearly average in a table but don't want to overwhelm you with it here.) With the birth of the NL (1876) it dipped to under 21, then quickly returned to the 23-24 range. When the rival leagues sprang up in the early to mid-1880s, again the age dipped down to under 22, but was back to the norm with the birth of the AL (1901). With the third major league (1914-15) and World War I, the average rookie age again dipped down to almost 22. World War II caused the only upward spike (to 26!). The first round of expansion followed by the amateur draft, caused the last dip down to 22 and the first since 1885-87. The average age stayed below or around 23 under 1980. Since then it’s been slowly increasing and has been above 24 since 1991. The average age in 2003 was about 24.5.
The biggest influence outside of sudden expansions and/or wars has been the amateur draft especially when it first started. Also, expansion, either by adding new leagues or expanding existing ones, caused the age to lower until the last couple of rounds. Perhaps the depth of talent is such that in recent years the best approach is to look to veteran minor leaguers.
Finally, here are the debut ages by decade represented as a percentage of all rookies:
| Debut Age % | |||||||
| Decade | <18 | 18-19 | 20-21 | 22-25 | 26-30 | 31-35 | 35+ |
| 1870s | 1.33% | 10.89% | 20.44% | 30.89% | 11.11% | 2.67% | 22.67% |
| 1880s | 1.71% | 9.31% | 20.56% | 40.58% | 13.28% | 1.50% | 13.06% |
| 1890s | 0.86% | 6.28% | 20.57% | 45.69% | 17.61% | 1.60% | 7.39% |
| 1900s | 0.37% | 4.89% | 16.33% | 51.66% | 23.25% | 2.95% | 0.55% |
| 1910s | 0.83% | 7.57% | 23.22% | 51.03% | 15.65% | 1.81% | 0.13% |
| 1920s | 0.25% | 4.07% | 16.51% | 49.71% | 26.89% | 2.57% | |
| 1930s | 0.19% | 3.08% | 16.47% | 54.14% | 23.22% | 2.60% | 0.29% |
| 1940s | 1.46% | 4.11% | 14.04% | 42.72% | 32.19% | 4.62% | 0.86% |
| 1950s | 1.68% | 6.26% | 13.46% | 48.69% | 26.64% | 2.80% | 0.47% |
| 1960s | 0.48% | 9.59% | 22.30% | 52.76% | 13.91% | 0.72% | 0.24% |
| 1970s | 2.81% | 23.25% | 62.54% | 11.32% | 0.08% | ||
| 1980s | 1.17% | 12.55% | 68.52% | 17.56% | 0.21% | ||
| 1990s | 0.53% | 9.31% | 65.83% | 23.74% | 0.59% | ||
| 2000s | 0.13% | 8.49% | 63.24% | 26.49% | 1.39% | 0.25% |
As the majors became more organized the over-35 rookie died a quick death. The amateur draft brought a large number of rookies under 22 even as the under-18 set disappeared. Finally, over the last few decades, the younger (under 22) rookies have been disappearing and while the 22-to-25-year-olds have slipped slightly, they remain the most populous with 26-30 gaining strength.
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