Inequalities and trends in access to health insurance and essential public health services among internal migrants in china: 2013 to 2018

China launched a major health-care reform in 2009 aimed to provide all citizens with equal access to basic health care with reasonable quality and financial risk protection. Since then, China has made substantial progress toward Universal Health Coverage (UHC). However, the access of UHC among internal migrants might be disadvantaged compared with local residents. This study aimed to provide an assessment of inequalities and trends in internal migrants' access to Universal Health Coverage. Six rounds (2013-2018) of the China Migrants Dynamic Survey were used including 976,430 respondents. Financial protection was measured using the basic medical insurance enrollment proportion (BMIEP) and hospital reimbursement rate (HRB). Essential health services were measured using the standardized health record establishment proportion (SHREP) and standardized health education intervention coverage (SHEIC). The Erreyers Index (EI) and Wagstaff Index (WI) were used to measure socio-economic related UHC inequalities. The process of the Recentered Influence Function (RIF)-Ordinary Least Squares (OLS) method was used to decompose risk factors of the EI and WI. The average coverage rate of SHREP and SHEIC were 24.3% and 75.7%, respectively. The average coverage rate of BMIEP and the percentage of HRB were 87.4% and 58.3% respectively. Regarding inequalities, it was found that for SHREP and SHEIC, the general trends of inequalities raised while for BMIEP, the general trends decreased. Regarding HRB, it was less inequalities in 2018 compared with 2014. RIF-OLS regression showed that both individual factors and regional factors contributed to the inequalities in UHC among China's internal migrants. Progress has been made in financial protection of migrants as the high coverage of BMIEP and its decrease in inequalities as well as lower inequalities in 2014 of HRB compared with 2018. While challenges remained in the lower coverage rate of SHEIC and increasing inequalities of SHREP and SHEIC. Policy efforts on narrowing down both individual and regional inequalities should be put forward.