Statistics New Zealand is the country's major source of official statistics of the people, the economy and the environment. If you would like more specific statistical information about New Zealand, you can access their site from the link below:
Statistics New Zealand
It's also possible to build your own demography data sets using the Statistics New Zealand Table Builder Tool.
The interactive Horowhenua District Economic Profile can be accessed here.
Infometrics provides a Demographic Profile for the Horowhenua District,available on here and can be used as a tool for visualising demographic data that is freely available in the Census.