Urban Sustainable Index (USI) 2013 builds upon the work carried out in USI 2011. USI 2013 has expanded and upgraded the indicators used in USI 2011. The analysis deploys 23 metrics, which cover four categories: economy, society, resources and environment. Ranked 185 cities, of varying sizes and at different stages of development, by their level of sustainability from 2005 to 2011. To ensure data was available, as well as to reflect the full landscape of Chinese cities, sample includes all levels of cities from municipalities directly under the central government, to county-level cities with populations ranging from 200,000 to 20 million.