People 60 years and older are expected to make up nearly half of China's population by 2050, according to estimates from the United Nations.Cheng Xin/Getty ImagesChina has no choice but to keep raising the retirement age for workers, according to Yi Fuxian.The nation has a demographic crisis, which is straining the pension system, the researcher said.China could have 475 million people over the age of 60 by 2050, per UN estimates.China has a retirement crisis on its hands, and the nation will probably be forced to keep raising the retirement age for workers to stave off demographic imbalances, according to a demographer.Yi Fuxian, a researcher whose book on China's demographic problems was previously banned in the country, cast a dark outlook for the nation's demographic future, with its population aging and its workforce rapidly shrinking.