Where Should Urban Planners Focus Their Attention?

For all its faults, Japan’s top-heavy, pro-development style of land use regulation has produced a remarkable urban structure, making Tokyo the undeniable king of the megacities, while avoiding the profound unaffordability of Hong Kong, Vancouver, New York and London.

It is time for planners to abandon abstract objectives and to focus their efforts on two measurable outcomes that have always mattered since the growth of large cities during the 19th century’s industrial revolution: workers’ spatial mobility and housing affordability.As a city develops, nothing is more important than maintaining mobility and housing affordability.Mobility takes two forms: first, the ability to travel in less than an hour from one part of a city to another; and second, the ability to trade dwellings easily with low transactions costs.Housing mobility allows households to move to the location that best maximize their welfare. Affordability is the ability for any urban household to be able to rent a dwelling for less than a 25% of its monthly income, or to buy one for less than about three time its yearly income.The mobility and affordability objectives are tightly related. A residential location that only allows access to only a small segment of the job market in less than an hour commuting time has not much value to households, even if it is theoretically affordable.For instance, the government of South Africa has been building several million units of heavily subsidized “affordable” housing in areas that require long and expensive commute – transport costs representing in some cases more than 50% of a worker salary. In this case, affordability without mobility is only a poverty trap. Affordability and spatial mobility are therefore inseparable objectives.