The gap between how much New Zealand Superannuation pensioners receive and how much they spend has widened significantly and many are working beyond the age of 65 to pay for the shortfall.
The Retirement Expenditure Guidelines calculate what retirees spend to maintain either a "no frills" retirement, or a more fulfilling "choices" lifestyle which includes some luxuries.
Costs were calculated by the Westpac Massey Fin-Ed Centre for one- and two-person households in Auckland, Wellington and Christchurch, and provincial areas.
The report, which covered the 12 months to June last year, showed all households, including those groups with a "no frills" lifestyle, now had a gap between what they were spending and what they received from NZ Super.
Report author Claire Matthews, from the Massey Business School, said it was not necessarily cause for concern.
The gap had at least doubled for most households, which was a significant change from the previous reports.
"But, to some extent, this reflects households being better prepared for retirement, allowing them to top up their superannuation payments to give them the lifestyle they want."
For the first time, the Retirement Expenditure Guidelines included information about income for retired households, to complement information about how much they were spending.
It showed about half of retirees living a "choices" lifestyle were still working - at least part time - while the rest were accessing savings or investment income, she said.
It seemed reaching eligibility for NZ Super did not mean stopping work for many.
While it could mean a change in working patterns and styles, semi-retirement offered people options for topping up their superannuation and saving more for when they stopped working completely, Dr Matthews said.
For some, the report will contain some surprises.
One-person households receive $390.20 weekly from NZ Super and two-person households receive $600.30. Super is paid fortnightly.
The report estimates total weekly expenditure for a single-person household on a no-frills budget is $590.44 in metro areas and $561.04 in provincial areas. On a choices budget, the spending is $1175.17 in metro areas and $824.16 in provincial areas.
For a two-person household, the metro no-frills budget is $872.22 and $1399.72 for choices. The provincial figures are $621.48 and $1104.78 respectively.
The report said superannuitants were disadvantaged by the high rate of inflation in the three months ended March 2017, which was not included in the annual adjustment to NZ Super rates until April this year.
Income from pension and superannuation was a much greater proportion of total household income for no frills households.
Income from pension and superannuation was also a much greater proportion of total household income for provincial households.
On average, all household groups had some level of other regular income, the report found. The key sources of other income were wages and salaries, and investments.
