2.3. Data acquisition and processing Social and economic data were mainly from each city’s Statistical Yearbook, China City Statistical Yearbook, China EnergyStatistical Yearbook, China Statistical Yearbook, and Statistical Communiqué on Economic and Social Development. Environmental data were obtained from the published literature, eachcity’s Statistical Yearbook, and China Statistical Yearbook on Environment (the data sources of each indicator were listed in theAppendix). For missing values, we used the first order regression tofill the gaps within a series based on closest available data points(Emerson et al., 2012).