Leung Chun-ying wants to ban mainland mothers from giving birth in Hong Kong's private hospitals.
He really hasn't thought this one through.
On Monday, the incoming chief executive said he would forbid mainland mothers who were not married to Hong Kong residents from giving birth in the city's private hospitals next year.
It's clear enough why he said it. He knows people are upset at all the recent stories about hordes of pregnant mainlanders overrunning Hong Kong's maternity wards and crowding out local mothers. And he thinks banning mainland mothers will be a popular solution to the problem.
As usual with matters like this, it pays to start by looking at the numbers.
As the first chart below shows, there has indeed been an explosion in the number of mainland mothers giving birth in Hong Kong.
From fewer than 8,000 in 2001, the number of babies born to mainlanders shot up to more than 43,000 last year, almost half of all children born in Hong Kong.
But dig deeper and the stories about mainlanders swamping facilities meant for locals look less than convincing.
For one thing, relatively few mainland women give birth in Hong Kong's public hospitals. Despite all the stories about mainlanders overwhelming the city's health services by turning up in labour at accident-and-emergency departments, there were only 1,656 cases of emergency-room deliveries by non-residents last year - just 0.07 per cent of accident-and-emergency department admissions.
According to government figures, a further 8,800 or so mainland mothers booked public maternity beds in advance. Of those, roughly one third were married to Hong Kong permanent residents.
That leaves just 6,000 birth tourists from the mainland who gave birth in the obstetric units of public hospitals. That's a sizable number, but it's only a small proportion of last year's 47,000 public hospital births, the vast majority of which were to local women.
In any case, the number will fall this year, after the government allotted just 3,400 public hospital places to mainland mothers.
So if public obstetric units are struggling to cope, it's not altogether fair to blame mainlanders. In fact, the blame lies more with the Hong Kong government.
As the first chart shows, over the ten years to 2004 the number of babies born each year to Hong Kong residents followed a steadily declining trajectory, falling by some 25,000. Assuming this trend would continue, the government responded by closing down the obstetric units of some public hospitals.
But the trend reversed, and last year, Hongkongers gave birth to more babies than at any time since 1997. As a result, the pressure on public facilities today owes more to government cutbacks than to birth tourists from the mainland.
That's because, unlike locals, the vast majority of mainland mothers pay top dollar to give birth in the city's private hospitals. Of the 48,000 babies born last year in private hospitals, 70 per cent were born to mainland mothers.
As a result, if C.Y. bans mainlanders from giving birth in private hospitals next year, he will condemn those beds to remaining empty and those expensive facilities to going deeply underutilised.
That would be singularly pointless, but there is also another reason Leung might want to reconsider his ban: the Hong Kong government's plans for the future - including its home-building scheme - rely on those babies.
The government expects Hong Kong's population to climb by almost 2 million over the next three decades, to reach 8.9 million by 2039. But its projections assume an average birth rate of 93,000 a year, just short of last year's total, as well as net immigration of almost 30,000 a year.
As the second chart shows, a ban on mainland birth tourists could reduce the city's population growth by almost one million. And if the net immigration rate remains constant, population growth will fall by nearly 1.5 million compared with the government's forecast.
If C.Y. contemplates the effects of such a big shortfall on the city's economy - and its property prices - perhaps he will be moved to reconsider his ban.