Net Internal and International Migration by Territorial Authority Area

These maps provide an indication of the relative percentage contributions of net internal migration and net international migration to the total population change of each territorial authority area, between each of the three census periods 1996-2001, 2001-2006 and 2008-2013. The data are drawn from the MBIE-funded project 'Nga Tangata Oho Mairangi' (NTOM) (The Impact of Demographic Change on New Zealand's Communities) led by researchers at Massey University, the University of Waikato, and Motu between 2012 and 2014 http://www.ngatangata.ac.nz/massey/learning/departments/centres-research/ntom/ntom_home.cfm. The data were generated by Professor Natalie Jackson and Ms Shefali Pawar of NIDEA (National Institute of Demographic and Economic Analysis) via the development of a Demographic Accounting Model.

The Demographic Accounting Model applies a step-wise process to Statistics New Zealand data on births, deaths, internal arrivals and departures, overseas arrivals, and total (net) population change, to generate, as residual categories, values for net migration, overseas departures, and net overseas migration. First, for each area, deaths are subtracted from births to generate natural increase (and natural decrease where it occurs). Second, natural increase is subtracted from net population change to generate net migration as a residual. Third, internal departures are subtracted from internal arrivals to generate net internal migration. Fourth, net internal migration is subtracted from net migration to generate net overseas migration as a residual. Fifth, overseas arrivals are subtracted from net overseas migration to generate overseas departures as a residual.

Methodological notes: The internal and overseas arrivals migration data were originally sourced from Statistics New Zealand and are based on the Census question ‘where did you usually live five years ago?’ Because some people fail to provide this information on their census form, a methodological decision was made to prorate the data for those people according to the local (regional or territorial authority area) distribution for those whose address five years ago was stated.

Disclaimer: The methodological assumption that those who did not specify where they lived five years ago have the same residential distribution as those who did specify their previous address, may be incorrect. We took this approach because it is preferable to calculating movements based on ‘known’ previous residence only, as these proportions differ substantially for each region and territorial authority area. The resulting data should thus be viewed as a best approximation of the situation, and will differ slightly from the raw data that Statistics New Zealand publishes, and other analysts may generate.