The number of overstayers in New Zealand has almost halved in the past 15 years.
The estimated number of people who had stayed in New Zealand after their visa expired stood at 10,848 in January, down from 20,657 in 2000.
Immigration Minister Michael Woodhouse said staff were working harder on identifying genuine visitors before visas were issued, and overstayers were being encouraged to leave voluntarily to reduce the likelihood of their being refused re-entry.
He said while compliance staff numbers had increased, people leaving voluntarily had reduced deportation costs from $3 million to $1.3 million a year.
Although overstayers from India and China had bucked the downward trend, with Chinese overstayers up 119 per cent since 2000, Mr Woodhouse said those numbers were also down over the last decade.
"You have to put that in the context of the far greater number of Chinese nationals coming to New Zealand for any reason - whether it's for tourism, for study, skilled work," he said.
"And I think the reduction in the overstayers generally is even more remarkable when you consider how many people are crossing our borders now compared to 10 years ago"
But immigration lawyer Richard Small said Mr Small said overstayers often had good reasons to stay that did not involve working illegally.
He said the government should consider the hidden stories behind the statistics, including those trying to stay in New Zealand to look after sick relatives, or because their homes had been destroyed by cyclones.
"People who for example are caring for terminally ill family members and for whom there is no family visa and no option," he said.
"We might be talking about people whose home island - in the last three years we have had three or four devastating cyclones in the Pacific - is no longer viable."
He said he could see no public policy reason why New Zealand should not copy Australia's carer visa to allow a lawful avenue for people who offered a benefit to New Zealand by caring for relatives who would otherwise need care from their district health board.
He added that the number of children born in New Zealand, but who were not citizens, could add hundreds - or even thousands - to the estimates of overstayers.