KEY POINTS:
A massive shift of women into paid work over the past 20 years has left the average New Zealand family no better off.
A research project led by Prime Minister Helen Clark's husband, Auckland University sociologist Peter Davis, has found that the median family income, after adjusting for inflation and family size, was just over $37,000 a year in 1981 - and was still just over $37,000 in 2001.
In the same period, the proportion of working women rose from 47 per cent to 61 per cent.
The increase in women was offset by a 20 per cent drop in male fulltime employment, as men moved into self-employment and part-time work and on to benefits.
Families on middle and low incomes have ended up merely holding their own, while high-income families are better off.
The "Family Whanau and Wellbeing Project", funded by the Foundation for Research, Science and Technology, is using data from the past five Censuses to develop ongoing measures of family wellbeing.
Professor Davis told a Sociological Association conference in Hamilton this week that each Census cost $25 million, but until now the Government had not got that value of data from it.
A project statistician, Mark Wheldon, said the new measure of median family income could only be approximate because it was taken from data about Census income bands such as $15,000 to $20,000.
The measure then adjusts the Census median over time for changes in consumer prices and families' size and structure, so that it is not affected by social changes such as the trend towards more sole-parent families.
"Family" was any set of one or more adult caregivers with children.
The measure shows that the median gross income of all families dropped from $37,463 in 1981 to a low of $33,227 in 1991, before recovering slowly to $37,665 in 2001.
A sociologist in the team, Gerard Cotterell, said other measures also showed that real wages had been static or falling over the past 20 years.
Benefit levels were cut in the late 1980s and particularly in 1991 and had never recovered in real terms.
"It's kind of stunning," he said.
"Income inequality has increased in Western countries.
"What's scary in New Zealand is that it hasn't got better under Labour. There are more people in employment, but it's low-paid employment."
