Demographia, a consulting company in Illinois, released a survey of housing affordability for the third quarter of 2010.  Not suprisingly, US homes were the most affordable at 3x median income. 

Hong Kong's economy is growing based on China trade, and housing prices there have grown 50% in the last 24 months.  The former British colony has always been pricey, but at 11.4x median income it's now unchallenged as the least affordable housing market in the world.

Surprisingly, though, Australia has the least affordable housing among English speaking countries, at 6.1x median income.  That country also has a growing economy based on China trade, but some of the priciness may be attributable to the fact that 85% of Australians live within 50 miles of the coast. Coastal property tends to be more expensive worldwide.  (The survey was taken before the recent floods in Australia.)

While the U.S. is the most affordable overall (led by Atlanta at less than 3x), four markets in California (San Francisco, San Jose, San Diego and Los Angeles) are all at or above 5.9x.  New York, at 6.1x, is the fourth most unaffordable city in the U.S. and tied with Australia.   All five of the priciest markets in the U.S. are coastal.

The report considers 5.1x or greater severely unaffordable.