Chinanews, Beijing, October 22 - According to the result of the research project: “Estimation of Future Population and Multi-regional Human Capital in China”, conducted by the Institute of Population of Peking University, the natural population growth rate of Beijing has remained zero for 5 years. Taking migration into consideration, the population in Beijing might reach 20 million by 2020.In the past 50 years, the total population in Beijing has increased by more than 10 million, with immigrants as the major source of such growth.It is estimated that the 2008 Olympic Games will attract more people to migrate to Beijing. At present, there are 13-million-odd people living here.The project report suggests that Beijing should control the number of immigrants at 4 -5 million annually from now on.