A typical retired household here draws a monthly income of $1,735, half of which comes from investments and contributions from family members or friends.
A retiree household living in a three-room flat spends an average of $1,000 every month, of which a third goes to food and another third to housing, utilities and health expenses.
These snapshots of the average retiree's income and spending patterns have been captured for the first time in the latest Household Expenditure Survey, which polled more than 11,000 households.
The number of retiree households, defined as those comprising solely non-working people aged 60 years and over, has more than doubled in the last 13 years to 77,481. About 40,000 of them live in three- or four-room flats.
The retiree households have also been found to form a quarter of households in the bottom fifth of the population where income is concerned.
"The data is interesting as it is rare but it is insufficient for planning purposes," said Ms Peh Kim Choo, director of the Hua Mei Centre for Successful Ageing under the Tsao Foundation, which works closely with the elderly.
"Nowadays, post-retirement periods can stretch to 30 years so it will be good to know the costs needed for different retirement phases and whether those needs are being met."
The Department of Statistics, which conducted the survey during October 2012 and September last year, said the majority of these elderly households fell under the lower-income groups because they do not get income from work. Some may rely on children living elsewhere or social support to meet their needs while others finance their retirement using savings and investment returns.
Retiree households are also spending more every month. They shelled out an average of $1,700 last year, compared to $1,300 five years ago.
However, the bottom fifth of these households spent only $480 a month, compared to $4,120 for the top 20 per cent.
The divide that has emerged in the retiree class is also apparent when income levels are considered.
On average, those who retire in condominiums and other non- Housing Board apartments have a monthly income of $3,851 - six times that of those who live in one- and two-room flats, and more than double that of those staying in five-room and executive flats.
But this gap is not as wide as that between the poorest and the well-heeled segments in the general population. The survey found that households in condominiums and other non-HDB apartments earn an average of $20,536, about 10 times the income of those in one- and two-room flats.
Experts say that the gap between these groups narrows in retirement because people stop working.
"It's largely because of the loss of income from work, which hits richer people far more as a proportion of their income than poorer people," said Assistant Professor Walter Edgar Theseira of Nanyang Technological University.
"In retirement, the rich generally have investment income streams to fall back on, whereas poorer retiree households are very dependent on government transfers, subsidies and family contributions."
National University of Singapore sociologist Paulin Straughan also noted that the lowest-income households actually spend more than they earn each month, while even those who live in condominiums and other apartments are earning just $428 more on average than they spend.
This is worrying, she said, because health-care expenditure tends to go up as the population ages. "(The latter) are just about able to cover their expenses. All it takes (to put them in the red) is for expenses to go up when they fall ill."