The main reasons New Zealanders gave for not voting in the last two general elections were that they didn't get round to it, forgot or just didn't care.
Statistics New Zealand figures show 21 percent of non-voters in 2011 gave these reasons for not taking part.
A further 7 percent did not cast a ballot because they felt their vote wouldn't make a difference, the New Zealand General Social Survey said. This group almost doubled between 2008 and 2011.
Age, income, and migrant status also made a difference to voting behaviour, the survey found.
Younger people were less likely to vote; 42 percent of people aged between 18-24 years said they didn't vote in the 2011 general election. People who feel they don't have enough money to meet their daily needs are also less likely to vote.
Recent migrants had low voting rates, while migrants who had been in New Zealand for longer periods had very similar voting behaviour as people born in New Zealand.
Chief Electoral Officer Robert Peden said voter turnout has fallen from more than 95 percent in the late 1980s to less than 70 percent at the last election.
Mr Peden said electoral experts from around the world will discuss declining voter participation at a forum in May.