ONCE, single Singaporeans could not buy a Housing Board flat. Not a new, subsidised one. Not one on the resale market.
Then, in 1991, the rules changed. Those aged at least 35 could buy three-room or smaller resale flats. In 2004, resale flats of any size were open to them.
However, the biggest shift came last July, when the Government allowed singles to buy new, subsidised two-room flats as solo purchasers.
And now, in no time at all, the bar of public expectations has been raised further. Singles are now asking, as two did in letters to The Straits Times Forum page: "When can we buy three-room subsidised flats?"
Two things have changed to nudge the HDB to provide for singles.
One is the recent move to make public housing more inclusive. The Government has long maintained a pro-family policy in public housing, which is implemented by the HDB.
Those who want to buy a new, subsidised HDB flat usually need to form a "family nucleus" - they can be a married couple, with or without children; a divorcee, widow or widower with children; or a single with one or more parents.
In 1988, then National Development Minister S. Dhanabalan had explained why singles would not be allowed to buy HDB flats: "While we cannot force people to stay with their families, public housing policy should not be such as to encourage them to move out of the family home."
But over the years, changing expectations caused the Government to relent. In 1998, the Government even gave singles aged above 35 a housing grant of $15,000 to buy resale HDB flats.
Seen in this context, letting singles buy new two-room flats is just the latest move in a two-decade-long journey towards making public housing more inclusive.
One consequence of letting singles buy subsidised flats is that an unmarried mother with a child will now qualify. Unwed parents with children were previously barred under HDB's pro-marriage policy.
The second thing that has changed since 1988 is land use. Back then, Mr Dhanabalan had argued that land-strapped Singapore could not afford to let every single have a place of his own.
But the country has apparently coped with its land shortage well enough to let singles buy resale flats, and now subsidised flats. Singapore has found many ways to improve land use since 1988 - not least in the form of taller HDB blocks - and might well find more in the decades to come.
So, in these changing times, should singles be allowed to buy larger subsidised flats?
The move is not, strictly speaking, necessary - certainly not in the way that, say, helping lower-income families get a home is necessary. Yet there are sound reasons to consider it.
First, some singles can do with more space. Forum page writer Justin Cheng notes that an elderly single who is ill may need caregivers who need their own living space and "should not be sleeping in the living room".
There is also a pro-family angle: Having a small flat could get in the way of getting hitched, as Forum page letter-writer Edwin Lim pointed out. A single with a new two-room flat must live there for five years before he can sell it. A small flat might hinder plans to start a family, should he get married within that period.
Second, singles should not be shut out of housing subsidies that their married friends get.
PropNex Realty chief executive Mohamed Ismail Gafoor voices a common concern - or objection - when he asks: "How much should the taxpayer subsidise singles?"
To that argument, singles have replied that they are taxpayers too, yet do not enjoy the various tax reliefs or government subsidies in areas such as education that couples with children do.
But the third, most compelling reason why singles could be allowed to buy three-room flats is demand. If demand for three-roomers tails off from families, why not let singles have them instead? This need not happen now, but in time to come.
In last year's Budget debate, National Development Minister Khaw Boon Wan noted that some singles had e-mailed him to ask even for five-room flats.
Instead of dismissing this, he said: "One step at a time. Let us do the two-room flats because let us assess the demand. Then we slowly liberalise from there."
This year, he said he had no immediate plan to let singles buy larger flats. He phrased it thus: "Given our limited resources, let me prioritise and give greater priority to the married couples first."
Framing the issue as one of priority suggests that once certain needs are met, others - including those of singles seeking larger flats - can be considered.
When might this be possible?
Last August, after the first Build-To-Order (BTO) exercise open to singles, Mr Khaw noted that the new policy had not affected first-timer families applying for two-room flats. There were fewer such applicants than units available to them.
If the minister's eye is on competition between singles and families, singles' three-room dream might become more feasible if families lose interest in such flats.
That trend seems likely.
The general preference today is already for four-room flats, and five-roomers if the family can afford it, says R'ST Research director Ong Kah Seng.
Of course, if demand for three-roomers falls, the HDB could simply build fewer such units rather than open them to singles, notes Mr Ismail.
Furthermore, there are various other groups whose needs arguably come first, from single-parent families to lower-income singles themselves, who may be happy with a two-room flat.
Says Mr Ong: "The current government focus is to help singles who find resale flats too costly, unaffordable. So a two-room BTO flat will match their requirements and affordability."
So for now, a three-room BTO unit remains an unattainable dream. But this may not be the case forever, not least given how far the Government has moved already.
After all, as Mr Ismail points out: "In the past, no one could even imagine that singles would get a chance to get a BTO flat."