The world would have 300 million more people today if China had not pursued its aggressive population control efforts, the Chinese government boasted yesterday, as the world population hit the 6 billion mark. Chinese Premier Zhu Rongji said China intends to continue its present family planning policy. A senior U.N. Population Fund official praised the nation for making progress in all categories outlined by the International Conference for Population and Development, including maternal mortality, infant mortality, female literacy, and school enrollment. An increasing number of Chinese couples are choosing to remain childless, particularly in cities, and many Chinese couples are also having their children later. China’s current population is estimated at 1.248 billion. Its growth rate dipped below 1 percent last year.