Hong Kong has emerged as the most unaffordable housing market among 367 metropolitan areas in nine countries, according to a survey by United States urban planning researcher Demographia.

In Hong Kong, median home prices were 19 times the median annual gross household income as at the third quarter of last year. This was up from 17 times in 2014 and the highest recorded in the 12 years of the survey.

A 430 sq ft flat would be expected to set a buyer back more than US$750,000 (S$1.1 million), according to data from the Hong Kong Property Review. However, analysts have predicted that Hong Kong's property bubble will burst as US interest rates rise. The government has also pledged to boost housing supply to meet demand, further prompting predictions for prices to fall, AFP said.

Sydney came in second and Vancouver, third. The survey covered Australia, Canada, Hong Kong, Ireland, Japan, New Zealand, Singapore, Britain and the US.

Overall, the most affordable metropolitan markets were in the US, which had a moderately unaffordable rating of 3.5 in all.

The survey considers median multiples of 3.0 and below as affordable; 3.1 to 4.0 moderately affordable; 4.1 to 5.0 seriously unaffordable; and 5.1 and above severely unaffordable.

Singapore was ranked fifth. Its median multiple was 5.0, similar to 2014 and an improvement over 5.1 in 2013, when it was first formally included in the survey.

This means median home prices here were five times the median annual gross household income at the third quarter of last year, making it "seriously unaffordable". However, Demographia noted the Housing Board's efforts at making housing more affordable.

The HDB here accounts for nearly 90 per cent of the owned market, the survey noted. So while the median multiple here is considered seriously unaffordable, housing affordability for new homes appears to be better as the HDB has increased production and reduced new home prices, it said. "One strategy (to improve housing affordability) has been to increase what are effectively 'across the board' subsidies for all new houses - not counting special grants, such as for first home buyers."

The price difference between a new Build-To-Order flat and a resale flat in the same location is about $150,000 to $180,000, excluding grants, ERA Realty key executive officer Eugene Lim told The Straits Times yesterday. Furthermore, new flats have the benefit of a fresh lease.

Private home prices declined 3.7 per cent last year, while HDB resale home prices slid 1.6 per cent.