"Fertility is one of the main ways through which the size and/or composition of a population may change. Statistics on fertility are required to provide basic demographic information, and to inform the study of differences and changes in reproductive patterns, family size and structure in various age, ethnic and other sub-groups, including geographic areas, of the New Zealand population. This information provides central government agencies, local authorities, health authorities, researchers, private organisations and businesses with valuable information required for planning current and future social and community services, facilities and products. A statistical standard for fertility is required to clearly define the concepts being measured and to ensure that collections of this data will be consistent across surveys and over time.
Fertility is a flat classification in number of children categories from no children to nine children plus a category for ten or more children. The classification has 11 categories – excluding residual categories."