Abstract
Background: Rural-to-urban migration has increased rapidly in China since the early 1980s, with the number of migrants reaching 376 million in 2020 (National Bureau of Statistics [NBS], 2020). Despite this sharp trend and the significant contributions that the migrants have made to urban development, migrant workers have had very limited access to the social insurance that the majority of urban workers have enjoyed. Methods: Based on the background of the social insurance system adjustment in Chengdu in 2011, we establish a difference-in-differences (DID) model to empirically test the impacts of change in social insurance policy contribution rates on migrant workers' social insurance participation rates, using the China Migrants Dynamic Survey (CMDS) data from 2009-2016.Results: The social insurance participation rate of migrant workers was significantly reduced after they are incorporated into the urban worker insurance system. Meanwhile, there is no significant change in the wages of migrant workers, but the working hours became longer and the consumption level turned lower. That is to say, simply changing the social insurance model of migrant workers from "comprehensive social insurance" to "urban employee insurance" reduces the incentives for migrant workers to participate in the insurance and harm the overall welfares of migrant workers.Conclusion: The design of the social security policy is an important reason for lower participation rate of migrants. Therefore, it is necessary to solve the problem of insufficient incentives through targeted social security policies. Specifically, the first is to formulate a social security policy contribution rate suitable for the migrants. The second is to establish a comprehensive social security policy and gradually integrate the social security system.