According to new data from the United Nations, fertility rates are on the decline and families are getting smaller.

The cost of living, job insecurity and housing costs are among the main factors preventing families from having as many kids as they would have wanted, new reports claim.

Massey University sociologist Paul Spoonley says women are also getting more educated and have more of a role in the workforce - and that's another factor.

"Women are having children much later in life - and so as we see that first child, the age of the woman for the first child is creeping up."

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