forewordfrom a moderately prosperous society to china dream  from substeces to a moderately prosperous society  comprehensive prosperity  the china dreamnew circumstances and challenges for populous china  fertility policies and population increase  downsizing of families and aging of population  large-scale population flow and migration  imbalance in gender ratio at birthpolarization and transformation of social structure  employment structure, urbanization rate and industrial structure  occupational structure and social stratification  income distribution and social polarization  social organization structure and social governance systemthe world's largest social security scheme  basic situation of the development of social security  before this century  social security system-building accelerated in an all-round way  establishment and improvement of the housing guarantee system  main issues and prospects in the 12th five-year plan periodeducation, health and human resources  reform and development in education  reform of the medical system and development of the medical and health cause  china's population quality and development of human resourcesconclusion