Fifty is the new 20 for South Korean workers, data shows SEOUL (Reuters) - Workers in their fifties outnumbered those in their twenties last year in South Korea, home to the world's fastest-ageing population, data showed on Thursday. People in their fifties accounted for 18.3 percent of the 16.5 million South Koreans with jobs in 2013, just shading the 18.2 percent of those in their 20s for the first time since the government began compiling the data in 2011, Statistics Korea said. A year earlier, twenty-somethings held 19.0 percent of the jobs in South Korea, while those in their fifties accounted for 17.6 percent. A government official attributed the rising share of older workers to an aging population, with former retirees returning to the labor force for financial reasons. Nearly half of older South Koreans live in poverty, and many take low-paying jobs in order to make ends meet. The overall number of working-age people in Asia's fourth-largest economy is on track to decline from 2017, according to the Organisation for Economic Co-operation and Development (OECD). South Korea also has one of the world's lowest birth rates, a growing burden on the economy as the number of retirees grows rapidly. Reporting By Kahyun Yang; Editing by Tony Munroe and Paul Tait