[U]sing the estimated pitch count formula, I calculated the average per start pitch count for all pitchers, and then grouped by the decade that the pitcher made his debut.

1870s 127
1880s 131
1890s 129
1900s 123
1910s 116
1920s 116
1930s 116
1940s 112
1950s 109
1960s 109
1970s 105
1980s 103
1990s 100
2000s 97

Yes, every decade from the 60s onward showed a drop, but there is a downward trend for the entire history of the sport. Pretty much at any time you could have compared the current generation to the previous couple and said ‘Why don’t these guys pitch as much anymore?’