As reported in Table 4 , the results become more strongly pronounced and more significant for both OPS and ERA dispersion in the later sample years ( 1965 -- 2009 ) .
The coefficients on the quadratic terms are not significantly different between the periods .
As reported in Table 4 , the results become more strongly pronounced and more significant for both OPS and ERA dispersion in the later sample years ( 1965 -- 2009 ) , although the coefficients on the quadratic terms are not significantly different between the periods .