Half of all Kiwi families that had babies five years ago suffered measurable material hardship during their babies' first year of life, a new study has found.
The Growing Up in NZ study, which is tracking 7000 babies born in Auckland and Waikato in 2009-10, has found that in the babies' first year:
• 50 per cent of the families said they were forced to buy cheaper food so they could pay for other things they needed;
• 18 per cent put up with feeling cold to save money;
• 13 per cent had gone without fresh fruit and vegetables so they could pay other expenses;
• 13 per cent had used foodbanks or food grants.
The study's associate director Dr Polly Atatoa-Carr said the results were surprising.
"We do know that in New Zealand we have quite a high proportion of children living in poverty or low income," she said. "But yes, I am surprised. I think it's an area that we need to find out a little bit more about."
Some of the figures in the study are in line with a Statistics NZ living standards survey in 2008, which found that 22 per cent of families with children said they found it difficult to keep the house warm in winter, 9 per cent said they could not keep main rooms warm because of the cost, and 14 per cent cut back or did without fresh fruit and vegetables "a lot".
The figures also reflect the fact that 16 per cent of the families were receiving income-tested benefits when the babies were both nine months and two years old, although about a third of families moved off benefits between those two surveys and another third moved on to benefits.
However the new study shows sharply increased use of foodbanks, up from just 8 per cent who said in 2008 that they "received help (food, clothes, money) from a foodbank or similar".
The new study is also believed to be the first to show that half of all families said they were forced to buy cheaper food to save money for other things.
Dr Atatoa-Carr said these findings might be partly due to the fact that the babies were born into one of the worst recessions in many years.
"We didn't intend to start a longitudinal study at the beginning of a global economic crisis, but it will provide us with a little bit more evidence about what that environment is doing to families," she said.
Full hardship data has not been published since the children were a year old, but it has just been collected again when the children were four and a half and will be published later this year.
However, income data shows that family incomes generally dropped sharply when the babies were born, as one partner generally gave up paid work to look after the child, and have partly recovered since then as caregiving parents - still usually mothers - began going back to work.
The proportion of families earning at least $70,000 a year dropped from 60 per cent before birth to 48 per cent when the babies were nine months old, but recovered to 54 per cent by the time the children were two.
On top of that, the general economic situation has improved. Statistics NZ surveys show that the proportion of all households saying their income was not enough to meet their needs rose from 16.2 per cent in 2007 to a peak of 18.5 per cent in 2010, but fell to only 12.9 per cent last year.