[stamped]University College London Penrose Papers[end stamp] Insert on p.4 Census returns, however, indicate that differential fertility has gradually developed in this country since about 1850. Insert on p.4 Physique is loosely but significantly correlated with intelligence, and yet there has been a steady increase in the average stature and weight of English working class children during the last fifty years or more.[superior 17] Insert on p.4 - and, according to population experts, it is likely to continue[superior 19,20] - [end]