Abstract: China's urbanization rate increased from 18% in 1978 to 52.57% in 2012, but the citizenization rate as indicated by the urban population registration (hukou) is only 27%. The gap between urbanization rate and citizenization rate is accounted for by the rural-urban migrants who live and work in cities without the social welfare provided by the city governments. Promoting the citizenization of rural-urban migrants is a long-term and arduous task. To some extent it will decide whether China's urbanization can proceed smoothly and sustainably. This paper studies rural-urban migrants who need to be citizenized. Some existing research has provided estimates on the total size and annual increase of rural-urban migrants who need to be citizenized nationwide. However, these studies generally contain no data on the population size at the provincial level and the geography distribution of such population. This paper tries to fill this gap. Based on the data from the Sixth Census in 2010 and the county-level population statistics published by the Ministry of Public Security yearly, we estimate the migrants' population size of each province and the proportion of migrants with urban hukou among total migrants (short for M_hM). The result indicates a clear difficulty for rural-urban migrants to get an urban hukou. Firstly, the annual increase of migrants who need to be citizenized is 15.76 million nationwide. The coastal areas have the highest annual increase in the size of migrant population. Inland areas take the second place. Coastal areas mainly receive inter-provincial migrants. The proportion of inter-provincial migrants is more than 70% in coastal areas such as Guangdong, Shanghai and Zhejiang as well as Beijing. In inland areas migrants mainly move within the same province. The proportion of inter-provincial migrants is less than 10%. Secondly, nationwide the M_hM is 40.85%, which means more than half of the migrants did not have an urban hukou in the cities they work. The migrants in inland areas can get the city hukou with the least effort. In Henan, Guizhou and Chongqing the M_hM is higher than 70%. The most difficult area to receive an urban hukou locates in the coastal area of southeast China. The M_hM of Shanghai, Zhejiang, Guangdong and Beijing are less than 30%. Inter-provincial migrants get urban hukou more easily than intra-provincial migrants. The M_hM of inter-provincial migrants is 2 percentage points higher than intra-provincial migrants. Thirdly, with correlation analysis of 10 influencing factors and the M_hM, we found that high cost of citizenization, especially the huge public spending required for providing social welfare for migrants; the unreasonable budget-sharing mechanism; and the rigid restrictions of the current policy on settling in cities are the main obstacles for migrants to receive urban hokou and social welfare. Based on these conclusions, some suggestions about the citizenization of rural-urban migrants are put forward. The current social security financing mechanism should be reformed to increase the proportion of financial expenditures of the central government. Meanwhile, the central government should make different settlement policies based on the migration characteristics and urbanization processes in different provinces. The inland areas should relax restrictions on settlement and allow more migrants to receive urban hukou. The coastal areas should link the financial subsidies with migrants' residence permits instead of hukou.

Key words: citizenization, rural-urban migrants, spatial difference, the sixth population census, urbanization