National Ethnic Population Projections

Methodology A special cohort component method has been used to derive the ethnic population projections. By this method, the base population is projected forward by adding new birth cohorts and calculating the effect of deaths, migration and inter-ethnic mobility within each age-sex group according to specified mortality, migration and inter-ethnic mobility assumptions. New birth cohorts are generated by applying specified fertility assumptions to the female population of childbearing age, and specified paternity assumptions to the male population. The method differs from the conventional cohort component method two respects: For each ethnic group, births are projected separately for women, and for men where the mother is not of that ethnic group. For example, Māori births have been projected separately for Māori women, and for Māori men where the mother is non-Māori. The projections allow for population change due to inter-ethnic mobility (i.e. people changing their ethnic identification over time). Fertility and mortality assumptions are derived for the purpose of projecting each population and should not be used as a precise measure of fertility or mortality differentials between ethnic groups. Ethnic Concept The ethnic concept used in these projections is the ethnic group or groups that people identify with or feel they belong to. Ethnicity is self-perceived and people can identify with more than one ethnicity. Ethnicity is different from ancestry, birthplace, and nationality. For example, people can identify with Māori ethnicity although they may not be descended from a Māori ancestor. Conversely, people may choose to not identify with Māori ethnicity even though they are descended from a Māori ancestor. See Review of the Measurement of Ethnicity or the ethnicity classification for more information about ethnicity including information about the Statistical Standard for Ethnicity 2005. European or Other Projections have been derived for the combined 'European or Other (including New Zealander)' ethnic group. Sufficient demographic data is available to enable projection assumptions to be derived for the combined ethnic group, but not for the separate 'European' or 'Other (including New Zealander)' ethnic groups defined in level one of the ethnicity classification. This approach is consistent with Guidelines for Using Ethnicity Data: 2006 Census. If a person belongs to both the 'European' and 'Other' ethnic groups, they have only been counted once. Almost all people in the 'Other' ethnicity group belong to the 'New Zealander' sub-group. Stochastic (probabilistic) population projections Stochastic (probabilistic) population projections are produced to give estimates of uncertainty, although these estimates are themselves uncertain. The stochastic population projections are produced by combining 2,000 simulations of the assumptions. These simulations can be summarised by percentiles, which indicate the probability that the actual result is lower than the percentile. For example, the 25th percentile indicates an estimated 25 percent chance that the actual value will be lower, and a 75 percent chance that the actual result will be higher, than this percentile. Nine alternative percentiles of probability distribution (2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97.5th percentiles) are available for the 2020-base projections. At the time of release, the median projection (50th percentile) indicates an estimated 50 percent chance that the actual value will be lower, and a 50 percent chance that the actual value will be higher, than this percentile. en-NZ