The average age of the country's registered population was 37 when the government started to compile the data in 2008. The number has been on a constant rise, with the 40-year mark topped in 2014, according to the data.
Among cities and provinces, Sejong in the middle of the country had the youngest population with an average of 36.8. It was also the only city that saw a decrease -- by 3.6 years -- compared to when the data was first gathered nine years ago.
The average age was highest in South Jeolla Province at 44.7.
South Korea is projected to become an aged society this year with the ratio of people aged 65 and older hitting 14 percent and emerging as a super-aged society with the figure hovering above 20 percent in 2026. (Yonhap)