Introduction

Urbanization is a risk factor for subjective well-being, and the situation in China is evidence of this general rule (Harpham, 1994; Marsella, 1998; Vlahov and Galea, 2002; Gong et al., 2012). Over the last three decades, China has witnessed the largest peacetime human migration in history and a simultaneous acceleration of urban expansion. In 1978, 17.92% of the population lived in urban areas; by 2016, the proportion had risen to 57.35% (National Bureau of Statistics of China, 2017). Between 1978 and 2010, the total number of cities in China increased from 193 to 658. Of these, the number of megacities increased from 2 to 16; large cities, from 27 to 124; medium-sized cities, from 35 to 138; and small cities, from 129 to 380. The number of townships leapt during the same period from 2,173 to 19,410 (Central Committee of the Communist Party and State Council of China, 2014). Despite the rapid growth in migration and urbanization, happiness in China plummeted (Brockmann et al., 2009). Many studies have reported high psychological distress among urban residents (Gong et al., 2012). In order to deal with this issue, it is necessary to investigate more closely how the process of urbanization is affecting the subjective well-being of millions of residents who are either new arrivals or established residents in the expanding cities.

Size of population, sources of population, and the distribution of population within the city are the first things that we should establish when researching a city (Park, 1915). In the past 30 years, the rapid migration and city expansion in China have led to significant changes in the urban population composition and characteristics (Chen and Chen, 2015). Studies on China's migration and urbanization have primarily focused on migrants who leave rural areas to work in urban centers. The rural-tourban migrant population is of great interest and concern. However, Webb (1984) suggests that the rural–urban division is not sufficiently nuanced and has limited utility: the region being studied must be defined by more relevant criteria, especially the detailed composition of the population. In an effort to establish such criteria, this chapter draws attention to urban populations with divergent pathways to urban residency.