There have been below average pitchers always. I have run the numbers, and the difference between the 33th and 67th percentile on qualifying pitchers have been about stable since 1950 (about 1.2 wins difference), even with more pitchers (55 on 1960, 92 on 2010). Furthermore, the WAR on the 67th percentile has also remained stable, at about 2.4. So, not much data to back the dilution theory.
Year | Pitchers | WAR 33 | WAR 67 |
2010 | 92 | 3.7 | 2.4 |
2000 | 87 | 3.5 | 2.1 |
1990 | 75 | 3.4 | 2.4 |
1980 | 89 | 3.4 | 2.4 |
1970 | 79 | 3.7 | 2.4 |
1960 | 55 | 3.3 | 2.3 |
1950 | 61 | 3.6 | 2.6 |