One other thing we do know is that the normalization we can do is of course relative to peers. Greinke had 96% of the IP total of the league leader this year, so he pitched about as much as anybody. Guidry had only 82% of the IP total of the league leader in 1978. We can't really compare what they did in terms of IP to one another since their eras are not the same, but what is clear is that 2015 Greinke's ERA+ is computed relative to contemporaries relative to whom he threw more innings than the contemporaries against whom Guidry's ERA+ was calculated.