Parameter estimates using different the sex-ratios (Female��Male) reported in Canada over the period from 1931 to 1980*.

*Values derived from reference [65] for the condition where (C = 0.5) and assuming the change in the environmental factor (whatever this is) has been steadily increasing (i.e., linear) over the time-interval (sd = standard deviation). The estimates for the parameters a and b trend downward in the more recent time-intervals because the definition of a unit of environmental change (see Table 2) becomes smaller with more recent observation periods. The other estimates are unaffected by this circumstance (see Equations 14, 17, and 21).**Values for the maximum value that C could take (see text); extrapolated backward to the (1941�C1945) time-period for comparison.