Senior citizens in South Korea accounted for more than 12 percent of the country's total population last year, data showed Thursday, indicating that population is aging at a fast pace. According to the data by Statistics Korea, 12.2 percent of the country's 50.2 million population were aged 65 or older in 2013, which is higher than the 11.8 percent tallied in 2012 and much higher than 3.8 percent in 1980.