A study of international housing affordability shows Port Macquarie is Australia's third most unaffordable market.

The Demographia International Housing Affordability survey for 2014 says there is no affordable housing in Australia.

It identifies 39 separate Australian markets, of which it rates 14 as seriously unaffordable and 25 as severely unaffordable.

The only Australian markets rated as less affordable than Port Macquarie were Sydney and Melbourne.

The Sunshine Coast and Gold Coast are next.

The rating is determined by dividing the median house price by the median household income.

Mining boom town Karratha in WA is rated as the most affordable Australian market.