Briefly describe the advantages of the "social insurance model of old-age insurance".

Answer: There are three advantages: First, the responsibility for pension insurance is shared by the government, employers and employees, which is conducive to risk diversification and financial stability. Secondly, it embodies the principle of harmonization of workers' rights and obligations, which is conducive to increasing the motivation of contributors. Third, because the fund is managed by the central government, and thus has a strong social mutual benefit, is conducive to the sustainable development of the pension insurance system.