Stats NZ is pleased with how many people filled out the Census - despite it having the lowest response rate for the past five surveys

Release of the results has been delayed until next year, after preliminary calculations showed around 10 percent of people didn't fill in their Census forms.

Deputy Statistician Denise McGregor says they're working on replacing the missing data.

She says they'll have to put imputation data in place.

The Statistics Minister says there'll be a review to look at why participation was so low.