Arya News - Rising government bond yields threaten higher borrowing costs and renewed volatility across South Korea’s economy and markets.
SEOUL – A surge in long-term US Treasury yields is driving up borrowing costs in Korea, lifting government bond yields and adding pressure on companies, households and stocks.
The spillover was on full display last week. As the US 30-year yield climbed to 5.33 percent, its highest since 2007, Korea’s 30-year government bond yield surged to a record 4.751 percent.
The yields have since retreated, but the underlying pressures — heavy US debt issuance, aggressive AI-related borrowing and weakening demand from foreign official investors — remain unresolved.
The episode highlights how quickly stress in the world’s largest bond market can reach Korea, where domestic inflation and a more hawkish Bank of Korea are adding to the strain.
What sent US Treasury yields higher?
The latest selloff has been concentrated in longer-dated Treasurys, with investors demanding more compensation for holding US government debt over decades. That extra return, known as the term premium, has become a key force pushing yields higher.
“Unlike in the first half, the rise in US Treasury yields so far in the second half can be seen as the result of a higher term premium rather than monetary policy expectations,” Samsung Securities senior analyst Kim Ji-man said in a recent report.
Washington’s widening fiscal deficit points to heavier Treasury issuance, while major technology companies are also borrowing aggressively for artificial intelligence investment. Six major hyperscalers issued $182 billion of bonds in the first half, 14 times the amount a year earlier, according to Samsung Securities, with more than 30 percent carrying 30-year maturities.
Samsung Securities said most of a $72 billion decline in foreign Treasury holdings in June came from central banks and sovereign wealth funds. Kim said structural pressures from fiscal deficits, bond supply and shifting demand “remain intact.”
Why Korea feels the pain
US Treasurys serve as a benchmark for global bond pricing, but they are not the only force behind Korea’s recent rise in yields.
Hur Joon-young, an economics professor at Sogang University, said domestic inflation and expectations for a more hawkish Bank of Korea have also pushed Korean yields higher. Still, Korea has historically shown stronger policy rate synchronization with the US when American rates are rising, partly because of capital flows.
“When US policy rates fall, the synchronization is relatively weak, but when US rates rise, it tends to be stronger,” Hur said.
On Aug. 18, Korea’s 10-year government bond yield jumped 6.9 basis points to 4.382 percent, while the 30-year yield surged 8.2 basis points to a record 4.751 percent.
The Bank of Korea on Thursday raised its policy rate by 25 basis points to 3 percent, adding another domestic source of rate pressure.
Higher market rates can lift funding costs for companies and households. The yield on three-year AA- corporate bonds stood at 4.5 percent Wednesday, while the average rate on newly issued fixed-rate mortgages rose for a 10th straight month to 4.76 percent in July.
Korea’s semiconductor-heavy market is particularly exposed, Hur said. Higher US rates could curb investment by US technology companies and weaken demand for Korean chips, while concerns over AI investment could trigger a correction in US stocks that spills over into Korean equities.
“If US companies cannot increase investment as much as expected because of the rate burden, that could mean less demand for Korean semiconductors,” Hur said. “When the US coughs, Korea could end up with the flu.”
That sensitivity was evident on Aug. 18, when the Kospi gave up an early gain of as much as 3.4 percent and closed 1.55 percent lower as Korean long-term bond yields surged and higher global rates and oil prices weighed on sentiment.
Will the relief last?
US long-term yields have retreated from last week’s peaks, helped by falling oil prices and expanded Treasury buybacks. The Treasury said Aug. 19 it would at least double the size of its long-end buyback operations, bringing total long-end buyback capacity before the next quarterly refunding announcement to roughly $30 billion, based on the announced schedule.
Still, that is well below about $70 billion of 20- and 30-year Treasurys scheduled for issuance in September and October alone.
“The Treasury’s intervention is only a short-term fix,” KB Securities analyst Lim Jae-kyun said, adding that further buybacks funded through the Treasury General Account would also provide only temporary support as federal debt and interest costs rise.
With the underlying pressures unresolved, Hur expects bouts of volatility to recur as external shocks from oil prices, geopolitical tensions or fiscal concerns trigger sharp repricing. Shifts in the investor base could amplify such moves, he added, saying more rate-sensitive holders such as hedge funds may sell quickly when yields start to rise.
For Korea, that means the risk may recede at times without disappearing.
“There seem to be more and more triggers that could send US Treasury yields sharply higher,” Hur said. “Rather than constantly weighing on markets, there will likely be episodes when the issue resurfaces. We seem to be moving toward a more fragile equilibrium.”
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