There is a dramatic escalation of house prices in many global cities around the world in the past decades. What is more serious is that these prices have risen faster than household incomes in some of these cities. According to Demographia International Housing Affordability Survey, the median multiple – the measurement of housing affordability defined by the ratio of median house sale prices to median household incomes – has recently significantly increased in popular global cities, including Hong Kong, Sydney and London. As a result, growing numbers of residents in these cities – especially those with lower incomes – have had to pay higher shares of their income for their rented and purchased housing and thus experience a burgeoning housing affordability crisis