just guessing since I want to see what LGO is gonna say but I thought it was above 150IP
heres what i found
Earned Run Averages were based on at least 10 complete games pitched (1900-49), at least 154 innings pitched (1950-60), and at least 162 innings pitched since 1961 in the AL and 1962 in the NL. In the strike years of 1981, '94 and '95, qualifiers had to pitch at least as many innings as the total number of games their team played that season