The country’s population totalled 51.74 million on November 1, 2021, down 91,000 from a year ago, according to Statistics Korea.
The population included South Korean nationals and foreign residents who stayed in the country for over three months, reports Xinhua news agency.
The number of South Korean nationals reduced 45,000 over the year to 50.09 million last year, while the reading of foreign residents retreated 46,000 to 1.65 million.
The population fall was attributable to the chronically low birthrate, caused by the younger generation who delayed or gave up on getting married or having babies amid the soaring housing prices and economic hardships.
Aging also contributed to the lower population.
South Korea was widely forecast to become a super-aged society in 2025, in which the portion of those aged 65 or higher reaches 20 percent of the total population.