Drawing on the data from the latest three decennial censuses, this paper analyzes the spatial pattern and influencing factors of China's population change since 2000. The results show that China's population becomes more spatially unbalanced, which is reflected by the persistent difference between the east and west areas, the widening gap between the south and north areas, and the increasing disparity between the central cities and peripheral counties. Natural environment, economic, amenity factors and the administrative hierarchy play significant roles in population change. However, their effects not only evolve with time, but also vary among regions at different stages of development. In the last decade, regions with a high rate of population growth have transferred from the coastal areas to the inland areas and from the plain areas to the mountain areas. The differences of public services among regions become an important factor for population growths, especially in the east China. Central cities become more and more attractive to population, showing the increased impact of state forces, which mainly happens in the middle and west China. The results can help understand the driving factors of population change, and provide references for promoting the balanced population development.

Fertility transition of ethnic minorities is an integral part of the demographic transition of China. Studying fertility transition among different ethnic groups offers a new perspective in understanding fertility transition in China. This study uses multiple waves of micro census to describe fertility transitions of different ethnic minority groups. Utilizing multilevel models, this study also identifies the between and within group determinants of ethnic minority fertility behaviors. Results show that similar to Han Chinese, ethnic minorities also experienced fertility decline over the past forty decades. Yet their rates of decline were modest. Most ethnic minority groups reached near replacementlevel fertility since 2000, and some saw modest increase in the recent decade. There exist heterogeneities within ethnic groups. Different ethnic groups exhibit different fertility patterns. The multilevel analysis results show that ethnicspecific traits had diminishing yet still significant impact on fertility behaviors. Within ethnic group differences account for a larger part of the total fertility variations.

This paper examines the heterogeneous effects of education and work experience on job quality of migrant workers measured from income, working hours, and social insurance in Chinese cities. Results show that both the years of schooling and work experience are positively correlated with the overall job quality. The years of schooling affect all three dimensions of job quality, while work experience does not significantly influence working hours. The marginal returns to years of schooling are 9 times higher than those to work experience. Further, education has indirect effects on job quality through influencing occupational levels and formal/informal employment while work experience does not. Education not only fundamentally sets the starting point of job quality by influencing the attributes of migrant workers' first job, but also indirectly affects the further improvement of job quality as indicated by the significant differences between the returns to human capital (i.e. years of schooling and work experience) in jobs at different levels.

Based on the 2015 Chinese 1% population survey, this study examines the spatial patterns of Chinese stem family and its influencing factors. It is found that there is significant heterogeneity among the distribution of stem families at the prefecture-level city with generally higher proportion of stem family in the south China and lower proportion in the north China. We further explore the spatial variation of factors affecting stem families using Geographic Weighted Regression (GWR) model. The results demonstrate that socioeconomic, demographic, and culture factors all play important roles in determining the distribution of stem families. The former two factors can exhibit opposite impact conditioned on the local culture and the development model of urbanization. Meanwhile, the impact of housing price is also divergent depending on the sensitivity of local housing market to the price change. These results suggest that the interplay of socioeconomic level, development mode, and cultural tradition ultimately shapes the pattern of Chinese stem family.

This study investigates the impact of human mobility on the spatio-temporal dynamics of COVID-19 spread by utilizing daily COVID-19 data of more than 300 cities in China. The spread of COVID-19 in China is characterized by a two-stage pattern, namely the inter-city transmission driven by human mobility in the first stage and the local transmission among family members in the second stage, which have further shaped the spatio-temporal patterns. The impacts of human mobility on the COVID-19 spread are featured by structural differences and dynamic patterns. Temporal movements including tourism and business travel are the main route of transmission at the beginning of COVID-19 outbreak, while internal migrants returning to their hometowns during the Chinese Spring Festival are mainly responsible for the peak outbreak in early February. Both survey data and big data have equally high statistical power in predicting and interpreting the spread of COVID-19, indicating that the combination of the twos strengths would contribute substantially to advancing quantitative research and improving social governance capacity.