The population of China's capital reached 16.95 million as of the end of 2008, up 620,000 from a year earlier, the Beijing Municipal Bureau of Statistics said.
One in four residents were migrants.
"The population in Beijing has been swelling rapidly over the past four years," said bureau spokeswoman Yu Xiuqin.
The increased number every year over the past four years "is equal to the population of a small or medium-sized city," Yu said.
Beijing's population was 15.38 million in 2005, 15.81 million in 2006 and 16.33 million in 2007. The 2005 figure was up 453,000 from 2004.
Yu said there were several challenges that required attention, such as resources and the environment, which were affected by rapid population and economic growth and social development.
(Xinhua News Agency January 26, 2009)