This form of tax is implemented in Sydney, Hong Kong, and in Pittsburgh, Harrisburg and many other cities in the state of Pennsylvania in the United States along with cities in Denmark and Finland (Box 4.3). A disadvantage of the tax could be the transaction costs of valuing urban land values independently from built structures (OECD, 2010a). In theory, by dropping the relative tax penalty for land development, owners are less likely to view selling-price appreciation as their primary asset, and unproductive speculation is reduced.