A total of 28 provinces were identified and rated in terms of economic development based on their 2015 Gross Domestic Product (GDP) per capita. To obtain robust estimates for each outcome at the subnational level, we removed seven provinces (Qinghai, Guizhou, Xinjiang, Chongqing, Tianjin, Beijing and Shanghai) with small sample size (e.g. fewer than 200 individuals) from provincial analysis.
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