In Hong Kong, Beijing and Shanghai, it now takes more than 30 years for an average household to buy a 90-square-meter apartment, making them among the cities with most unaffordable housing.

The ranking, compiled by advisory firm Oxford Economics, is based on price-to-income ratios across the world.

While four of the top five come from Asia, London, on fifth spot, is the highest ranked European city.

Now let's take a look at the top 10 cities with most unaffordable housing across the world.

10. Seoul

Samcheong-dong, dotted with hanok, traditional Korean housing, is becoming a residential area for upper class in Seoul, April 24, 2016. [Photo/IC]