It is increasingly unlikely that Statistics New Zealand will be able to plug the gaps in the data that's missing from last year's flawed Census.

The Government is pumping $6 million into fixing the issues, after 700,000 people didn't fill it out. It will also be giving Stats NZ an extra $10 million to get ahead of the next Census. 

The full results won't be released until mid-2020 and Statistics New Zealand is having to fill in 10 per cent of data itself.

Motu Economic and Public Policy Research executive director, Dr John McDermott, told Kate Hawkesby even if Stats New Zealand makes sensible technical adjustments, there will still be gaps.

"Some valuable microdata will be missing, it will be lower quality, and it will make it less valuable to researchers," he said.

McDermott said Statistic New Zealand's hands are tied because they don't have any other choice but to fill the data in itself.

He said the groups who are most vulnerable are also likely to be the ones who haven't filled out the survey, making it extremely hard for Statics New Zealand to cater to their needs.

"There are probably important groups that need public policy to help them, that is probably not filling in the data."

There will be parts of the population that are quite mobile, maybe even poor parts of the population who didn't fill it in so we don't know what the problems are."

"Those people who haven't filled it in, those communities are the ones who will suffer."

He said the census is incredibly valuable when it comes to addressing issues such as income inequality, migrant settlement, the gender pay gap and the housing market.

McDermott said there will be gaps when it comes to climate change as well.

Moving the next census forward would help researchers fill in the gaps, he said.