This rate surge won't cool as easily as 2023's — here are three reasons why

With the US 10-year Treasury yield approaching 5%, analysts at South Korean brokerages say this surge in long-term rates will not cool as quickly as it did in 2023.

Long-term rates soared to around 5% in 2023 before stabilizing rapidly, but conditions today are different. Bond supply pressure, resilient investment activity and geopolitical instability are all pushing rates higher at the same time. Analysts single out the Middle East war's direct impact on oil prices — and the inflation and monetary policy uncertainty that follows — as the most significant difference from three years ago.

The 10-year Treasury yield climbed to 4.821% during trading Wednesday (local time), its highest since November 2023. It pulled back slightly but held at 4.78%, remaining elevated. Markets widely expect the 10-year yield to breach 5%, with analysts forecasting a rate rise comparable in scale to 2023.

"The US 10-year yield, having cleared 4.8%, is now on course to test 5%," said Lee Sang-jun, a researcher at NH Investment Securities. "The 5% level on the 10-year was last seen in 2023, when the Federal Reserve raised its benchmark rate ceiling to 5.5%."

The starting point of the 2023 rate surge was not so different from today's. Treasury issuance resumed after the debt-ceiling deal, and the Treasury Department unveiled a borrowing plan larger than markets had expected, rapidly stoking fiscal concerns. Fitch's downgrade of the US credit rating and an expansion of coupon bond issuance compounded the pressure, putting the spotlight on long-term bond supply.

A strong economy also pushed rates higher. With employment and retail sales coming in stronger than expected, a perception spread that monetary policy was not sufficiently restrictive even as the Fed raised rates aggressively — fueling concerns that further hikes might be needed and driving long-term yields up.

That dynamic did not last. Doubts emerged about whether the consumer spending boom could be sustained, and when employment data subsequently softened, fears of an overheating economy faded quickly.

The decisive turn came when the Treasury announced it would raise long-term bond issuance by less than markets had anticipated and would increase the share of short-term debt, easing supply pressure on the long end. When the FOMC then sent relatively dovish signals, the 10-year yield fell roughly 60 basis points — one basis point equals 0.01 percentage point — within a month.

The question now is whether rates can be pushed back down the same way. Markets see three key differences this time.

The first is bond supply. The Treasury has already signaled its intent to reduce long-end supply pressure through measures such as long-term bond buybacks. Yet long-term yields keep rising, suggesting markets are more worried about the sheer volume of total Treasury issuance than about how it is distributed across maturities. Expectations that war costs related to Iran and other factors will force further issuance expansion are adding to the burden, as is a pickup in corporate bond issuance.

In 2023, markets were reassured by a shift toward shorter maturities and away from long-term bonds. Now, markets are pricing in a level of total supply pressure that maturity adjustments alone cannot resolve. It is America's enormous debt load itself that is weighing on the bond market.

"An expansion in Treasury issuance is unavoidable given tariff refunds and the costs of the Iran war," said Kim Il-hyeok, a researcher at KB Securities. "Markets are feeling a bond supply burden that cannot be resolved simply by adjusting the mix of maturities."

The second difference is the engine driving the economy. In 2023, consumer spending was the primary force behind economic strength. High rates could weaken consumption, and with it, expectations of a slowdown — naturally pulling rates lower.

Today, investment — particularly in AI and data centers — sits at the center of growth. US data center construction spending rose 6.23 percent month-on-month in July and jumped 35.5 percent compared with the end of last year.

The AI investment race is less sensitive to interest rates than ordinary consumer spending. With big tech companies pouring money into large-scale projects to secure market position, higher financing costs are unlikely to halt investment immediately. In this environment, economic concerns are unlikely to drag rates down quickly unless the next jobs report comes in significantly weaker than expected.

The third difference is that war is now directly affecting oil prices. The Israel-Hamas conflict in 2023 did not translate into sustained oil market instability. This time, the resumption of US-Iran hostilities has pushed West Texas Intermediate crude above $90 a barrel, and expectations for a normalization of the Strait of Hormuz are fading.

Whether this rate surge can be reversed as quickly as in 2023 is therefore uncertain. Bond supply pressure is greater, the economy is proving resilient on the back of AI investment, and the war is stoking inflation through oil prices. All three factors are simultaneously blocking rates from falling.

The implications for equities are clearly negative. If the 10-year yield climbs further past 5%, valuation pressure on growth stocks will intensify, and share price correction risks will mount as fiscal concerns and tightening fears compound each other.

Some analysts, however, caution against reading the rate rise as a signal of a sustained equity downturn. The fundamentals of the domestic stock market remain intact, and if the 10-year yield exceeds 5%, more active intervention by the US government could cap the advance.

"If the yield tops 5%, the US government could intervene promptly, and the fundamental conditions of the domestic market have not been impaired," Lee said. "While increased share price volatility from rising rates is unavoidable, the Kospi is expected to rebuild upward momentum through rate stabilization — via government intervention and confirmation of economic data — and strong semiconductor-centered fundamentals."