BEIJING, Jan. 19 (Xinhua) -- The population of Beijing fell 0.1 percent to 21.7 million as of the end of 2017, authorities said Friday.

Of the capital's residents, 86.5 percent live in urban areas, and 73.1 percent are between 15 and 59 years old, said Pang Jiangqian, deputy head of Beijing municipal bureau of statistics, at a press conference.

Beijing plans to cap its population at 23 million by 2020 to address "big city diseases," including traffic congestion and pollution.

To meet the target, Beijing has taken measures to move non-capital functions away from the city, such as relocating wholesale markets and closing polluting factories.