Following on the journal’s last "Population and Development Forum" on commemorating the 30th anniversary of the Open Letter, this issue of the Forum extends the discussion on significance of the Open Letter and the unique model of China’s birth planning and demographic transition. Three scholars, namely Yang Wenzhuang, Liu Shuang and Wang Jinying, have been invited to contribute to this discussion. Yang summarizes the history and changes of China’s birth planning policy, arguing that birth planning in China initially adopted an approach of family planning by government support, which was changed to state planning by coercive measures, further to policy adjustment and reform, and finally to one that is human-centered with unified planning comprehensively addressing population issues. Liu suggests that China’s birth planning be assessed in a historical perspective and placed in the context of societal changes, and its enormous demographic and socio-economic effects are largely positive and long-lasting. Wang have worked out quantitatively the demographic, economic and environmental impact of China’s birth planning with the options it offers for future social and economic development.