South Korea's population stands at 48.5 million, the 26th largest in the world, a United Nations Population Fund (UNFPA) report shows. The UN agency released its State of World Population 2010 report on Wednesday. 

Combined with North Korea's 24 million people, the Korean Peninsula ranks 19th in the world with a population of 72.5 million.

The Ministry of Public Administration and Security recently announced that South Korea's registered population surpassed 50 million. As the UNFPA's estimate is based on data over the past five years, there is a slight discrepancy between the figures.

According to the UN report, South Korea's population will likely continue to decrease due to the low birthrate, falling to 44.1 million or the world's 42nd largest by 2050. The nation's birthrate is 1.24 this year, lagging behind the world average of 2.52 and the 1.65 average of advanced economies.

Of 186 countries in the world, South Korea had the third lowest birthrate, trailing only Hong Kong with 1.01 and Bosnia Herzegovina with 1.22. But according to Statistics Korea, the country's birthrate stood at 1.15 in 2009.

The life expectancy for South Korean men reached 76.4 years, ranking 31st in the world, and 82.9 years for women, the world's 17th highest. Iceland has the longest life expectancy for men at 80.5 years, and Japan for women at 86.6 years. In North Korea the expected life span is lower than the world's average -- 65.5 years (118th in the world) for men and 69.7 (125th) for women.

Meanwhile, the world's population rose 79.3 million to 6.99 billion this year. China is the most populous nation with 1.35 billion people, followed by India with 1.21 billion and the U.S. with 317.6 million.