South Korea's reliance on trade fell to an all-time low in a decade last year, data showed Tuesday, but there are lingering concerns that Asia's fourth-largest economy remains vulnerable to external factors.

The proportion of South Korea's trade to its gross national income (GNI) -- a gauge of a country's trade dependence -- stood at 80.8 percent at the end of last year, down 5.9 percentage points from 2015, according to data compiled by the Bank of Korea.

The ratio jumped to 104.5 percent in 2008 in the wake of the global financial crisis and surged to 113.5 percent in 2011 before falling to 98.6 percent in 2014 and 86.7 percent in the following year.

The latest decline is attributed to a fall in global oil prices. South Korea imports crude oil that is refined in the country and exported as petrochemical products.

A separate data compiled by the Organization for Economic Cooperation and Development, a group of 35 mostly rich nations, showed that South Korea's reliance on trade is much higher than that of the United States and other advanced countries.

The proportion of South Korea's trade to its gross domestic product came to 84.8 percent in 2015, compared with 28 percent in the US, 56.8 percent in Britain and 61.4 percent in France.

The BOK said external factors such as a US rate hike and Britain's negotiations to formally leave the European Union could have an impact on the South Korean economy. Exports account for about half of the South Korean economy.

Experts said South Korea should boost domestic demand amid uncertainties over trade protectionism and Seoul's possible designation as a currency manipulator by Washington.

South Korea was put on a monitoring list by the US Treasury Department last year due to a significant bilateral trade surplus with the United States and other factors. The US government is expected to unveil a list of currency manipulators in April.

Bank of Korea Gov. Lee Ju-yeol has said there is a slim chance that South Korea will be labeled a currency manipulator, although the country should not let its guard down on the matter. (Yonhap)