The Office for the Community and Voluntary Centre (no, I didn't know they existed, either) in a paper entitled, How do New Zealanders Give? Ethnicity and Income Research Supplement, tells us that:
No matter their ethnicity or income level, approximately three quarters of New Zealanders support the community and voluntary sector in some way.
In 2007, three quarters (75.4%) of people 10 years and over supported the community and voluntary sector. This was by any combination of giving, volunteering or other support (such as purchasing products). When compared to this population average, the differences between ethnic groups or different personal or household incomes are relatively small.
Besides this paper, which gives some extensive information on who gives to whom, there are four reports on Generosity by the same department. These have been coming out over the last couple of years, (the latest arrived only last month) and can be found here. The papers ask:
What do we mean by generosity?
What value do we place on generosity?
What do we know about generosity?
What can we do to promote generosity in New Zealand?
None of the papers are lengthy, but they have some interesting things to say about the state of generosity in NZ (pretty good) and our attitudes towards it.