Studying population flow patterns is essential for comprehending regional population changes and economic and social development trends. Using data from the sixth and seventh national population censuses to classify China's interprovincial population flows into four types: rural-urban, rural-rural, urban-urban, and urban-rural, this paper analyzes the spatial characteristics of population flow networks and their influencing factors using a spatial autoregressive negative binomial model. The results show that: The proportion of rural-urban and urban-urban population flows has increased, while the proportion of rural-rural population flows has decreased. Rural-rural and rural-urban population flows tend to move from west to east, while urban-urban and urban-rural population flows are diverse and bi-directional. China's population center is shifting from a single city (province) to an urban agglomeration. While economic factors play a significant role in rural-urban and rural-rural population flows, the factors influencing urban-rural and urban-urban population flows are complex and diverse. The degree of influence of economic factors on these flows is weakening.

Population agglomeration is the foundation of urbanization. However, lots of migrants in China returned to their hometowns. Housing prices and house ownerships are two crucial factors in determining whether floating population would return. Although a vast body of literatures have analyzed various factors in return migration as well as the effect of housing prices on migration and settlement intention, few studies have focused on return behaviors. Employing China Household Finance Survey, we examine the effect of housing prices and house ownerships on the return behavior of floating population. Results from IVProbit model show that (1) the increase in housing prices crowds out floating population to return; (2) owning houses in their host cities reduces the chance of return for the homeowners and weakens the crowdingout effect of high housing prices; (3) the effects of housing prices and house ownerships on return decision are varying among the locations and the scales of the host city. Our findings have important policy implications for advancing urbanization strategies.

Family income largely affects fertility behaviors under the universal twochild policy. The Fifth Plenary Session of the 19th CPC Central Committee proposed to reduce the cost of fertility, parenting and education. Using CFPS data collected before and after the recent family planning policy change, this research develops a twochild family income conversion sub matrix decomposition method, and empirically analyzes the characteristics of two-child family income mobility. A binomial logistic regression model is established to analyze the factors influencing the income mobility of twochild families. The results show that: (1)During the relaxation of fertility policy, the absolute income of two-child families has moved downward, and the speed of movement has increased. The possibility of income rank downward mobility has also increased.(2)The impact of having two children on income mobility differs across families in different income groups. Middleincome groups are the most affected while the highincome group is the least affected.(3)In addition to the individual and households' characteristics, the imbalance of economic development and urbanrural differences are still the important macro factors affecting the income mobility of two-child families in China.