All data in this report is based on Census Usually Resident Population counts with the exception of the population projections. The projection figures used are those of the medium series which are have their base as the estimated population as of June 2006.
Due to the policy of low level rounding by Statistics New Zealand figures may not sum to totals or match equivalent figures elsewhere in this or other reports.
Ethnicity figures are based on total responses rather than prioritised or sole classifications. Pakeha in this report refers to the combined grouping of European and Other (dominated by ‘New Zealander’ responses) L1 ethnic groupings. Where ethnic groups are presented as a proportional figure, the proportion is a function of the total resident population unless otherwise stated.
The cartograms in this report were produced using the Cartogram Utility for ArcGIS distributed by Environmental Systems Research Institute (ESRI). The utility generates Density Equalizing Cartograms using the methodology developed by Mark Newman and Michael Gastner at the University of Michigan (Michael T. Gastner and M. E. J. Newman, "Diffusion-based method for producing density-equalizing maps", Proceedings of the NAS, May 18, 2004, vol. 101, no. 20, pp 7499-7504).
Density Equalizing Cartograms modifies the size of an area (eg. CAU or DHB) in proportion to another attribute, such as total population. The outcome of which is the creation of equivalent density areas, that is, an area twice the size of another will have approximately twice the population. The methodology employed preserves as far as possible the overall shape of an area, and critically, neighbouring boundaries are retained (no gaps, no new neighbours)
Within each map the density of whatever is being displayed is ‘equivalised’ so that patterns better reflect what is being mapped rather than inherent topography. It is important to note that the total area of each cartogram in the report is approximately the same irrespective of the size of the population being displayed.
Ethnic resident populations with the equivalised density across different datasets are shown in Figure 129. Here the size of the areas are directly comparable across the different maps showing the distribution of the various groups across the region.
It should be noted that where the original areas vary dramatically in geographic or population size the cartogram densities will vary to some degree. In particular, CAUs in the Auckland region with very small or non existent populations may be overrepresented. At the national level the DHB cartograms were generated though the use of DHB sub regions (aggregated CAU). This was to preserve intra-DHB variation whilst ensuring a tight range of cartogram densities.
Many of the map colour schemes used in this report have been drawn from the ColorBrewer schemes developed by Cynthia Brewer at Pennsylvania State University (www.colorbrewer.org). Areal shading has been enhanced by offsetting border colour values in the HSV space.
The majority of maps in the report are determined using the Jenks Natural Breaks method, otherwise known as goodness of variant fit. This method is useful in displaying clusters of values or naturally occurring patterns.
