'Poorly defined': unknown unknowns in New Zealand Rural Health.

There is a considerable mismatch between the population that accesses rural healthcare in New Zealand and the population defined as 'rural' using the current statistics New Zealand rural and urban categorisations. Statistics New Zealand definitions (based on population size or density) do not accurately identify the population of New Zealanders who actually access rural health services. In fact, around 40% of people who access rural health services are classified as 'urban' under the Statistics New Zealand definition, while a further 20% of people who are currently classified as 'rural' actually have ready access to urban health services. Although there is some recognition that current definitions are suboptimal, the extent of the uncertainty arising from these definitions is not widely appreciated. This mismatch is sufficient to potentially undermine the validity of both nationally-collated statistics and also any research undertaken using Statistics New Zealand data. Under these circumstances it is not surprising that the differences between rural and urban health care found in other countries with similar health services have been difficult to demonstrate in New Zealand. This article explains the extent of this mismatch and suggests how definitions of rural might be improved to allow a better understanding of New Zealand rural health.