(1) In a paper read before the Institute in November 1933 (J.I.A. Vol. LXV, p. 38), Mr C. D. Rich showed how to calculate the inherent rate of growth of a population by combining in a single index the current data regarding mortality and fertility. Valuable though this index is in showing the true underlying trend at a particular point of time, it cannot be adapted (nor is it intended) to show the actual future populations at any particular time.
(2) It is the purpose of the present paper to make estimates of the population of Great Britain, according to age and sex, for certain future years, and in order to do this an attempt is made to forecast the probable future course of mortality and fertility in Great Britain, in the light of the experience of the past, and such indications as there may be regarding the factors which will influence the future.