BEIJING, Jan. 23 (Xinhua) -- The number of permanent residents in Beijing dropped 0.8 percent to about 21.5 million at the end of last year, official data showed Wednesday.

In terms of age composition, the number of permanent residents aged 15 to 59 exceeded 15.6 million, about 72.6 percent of the city's total population, according to the data released jointly by the Beijing Municipal Bureau of Statistics and the Survey Office of the National Bureau of Statistics in Beijing.

There are about 2.3 million permanent residents aged 14 and under, accounting for 10.5 percent, while the number of residents aged 60 or above is more than 3.6 million, taking up about 16.9 percent.

The urban population in Beijing is about 18.6 million, about 86.5 percent of the capital's total permanent population.

In 2017, the number of Beijing's permanent residents was about 21.7 million, 22,000 fewer than in 2016.

Beijing plans to cap its population as it seeks to address "big city diseases" such as traffic congestion and pollution.