Comparing Players Across Eras

A 3.50 ERA means something different in a high-scoring era than in a low-scoring one. A 25-point-per-game scorer means something different at a pace of 100 possessions than at 90.

Rule changes, equipment, training, strategy, and the size of the talent pool all move the baseline. Comparing raw numbers across eras compares the eras as much as the players.

The standard fix is to express performance relative to the player's own league and park, then set league average to a fixed value — usually 100.

That is what the "plus" statistics do. OPS+ of 140 means 40% better than league average after adjusting for park; ERA+ of 140 means the same for run prevention. A 140 in 1968 and a 140 in 2026 are genuinely comparable in a way that raw ERA never is.

Two honest limits:

• Talent pool depth. Being 40% better than average is more impressive when the league is deeper. Adjustment normalises the average, not the difficulty.
• Role changes. Pitcher usage, positional definitions, and shot selection have changed so much that some comparisons are between different jobs, not different players.

Era adjustment makes cross-era comparison possible. It does not make it simple, and anyone presenting it as settled is overselling.