Changing sex ratios in New Zealand: Real change or a statistical problem?

Abstract

In New Zealand, in all age groups under 20, and in key working age groups, historically there have been more men than women. Life table data suggest that, without migration, the number of males should remain greater than the number of females until around the age of 60 years. However, census data indicate that the number of New Zealand women residents relative to men in the broad 20-49 age group has been increasing since the 1980s. Given that birth ratios for New Zealand residents favour boys in common with international experience, the imbalance of women over men in the 20-49 age group has to come from four possible sources: 1) differential mortality; 2) more New Zealand born men leaving New Zealand; 3) a higher number of female immigrants; or 4) that statistical collections are undercounting men, and this undercounting has become progressively greater over the past 20 years. In this paper we focus on undercount and, through this investigation, raise some doubts about the validity of either a serious ‘man drought’ or a major 'surplus of women' in the population.