An analysis of the sources and magnitudes of inconsistencies between male and female net reproduction rates in actual populations

Summary Male and female net reproduction rates calculated from a given actual population generally yield different, i.e. inconsistent, annual rates of intrinsic growth. This inconsistency is due to the nature of the sex-age distribution of the population. The paper examines first the conditions which are necessary and sufficient for a population to yield consistent male and female rates, and secondly the factors which prevent actual population conforming to the conditions for consistency. These factors are shown to relate to the past behaviour of fertility, mortality, masculinity at birth and, in particular, to the effects on populations of external disturbances like wars and migrations. A detailed analysis of the importance of the various factors in causing inconsistencies between male and female reproduction rates is made by examining over seventy census populations and the importance of the magnitudes of the inconsistencies is indicated.