Migration and stability.

"In this endeavor to incorporate net migration in a model of population growth, we have found that when net maternity rates are held constant, birth trajectories can be traced in several examples. We have basically experimented with (a) unchanging age-specific net migration rates and also with (b) constant number of net migrants with unchanging age composition. In most cases, the birth trajectory approaches an exponential pattern of growth with two interesting exceptions. When the intrinsic rate of growth is negative, the population approaches stationarity in the second example. Also a linear trend is found in the same example, when the net reproduction rate is equal to one." (SUMMARY IN FRE AND ITA)