SHANGHAI -- China's eastern metropolitan of Shanghai saw its population shrink for the first time this century.

The city's permanent population, those who have lived there for six months or more, was 24.15 million at the end of 2015, marking a decline of 0.4 percent year on year, the city's statistics bureau said Tuesday.

The city has been a magnet for job seekers thanks to booming economy, but its aging local population and low birth rate have dragged down the growth figure.

Yet population experts believe last year's negative growth was mainly a result of the measures taken by the megacity to curb its population in order to alleviate the pressures on traffic flow and infrastructure.

Zhou Haiwang, a demographer with Shanghai Academy of Social Sciences, said the city had relocated many residents by phasing out obsolete industrial capacities and demolishing illegal buildings.

Zhou said the trend befitted the city's plan to limit its permanent population within 25 million by 2020.