Paraguay's biggest cities are located along the Argentina-Paraguay border: Asunción, Encarnación, Pilar and Ciudad del Este, the latter being the third most important free commercial zone in the world, only trailing behind Miami and Hong Kong. A large percentage of the population, especially in rural areas, derives its living from agricultural activity, often on a subsistence basis. Because of the importance of the informal sector, accurate economic measures are difficult to obtain. The economy grew rapidly between 2003 and 2013 as growing world demand for commodities combined with high prices and favorable weather to support Paraguay's commodity-based export expansion.