Bond vigilantes explained: how markets can push interest rates higher

The term bond vigilante was coined by economist Ed Yardeni in the 1980s in reference to investors who vote with their feet when they judge central banks or governments are being reckless or inflation is being mismanaged.

The idea is simple. When a government runs budget deficits investors think are unsustainable, bond investors sell. Selling drives prices down and because yields move inversely to prices, yields rise.

Higher yields mean a government’s borrowing costs go up, sometimes dramatically. If the rate rise is sharp enough and sustained, it becomes a constraint on fiscal policy.

In effect, bond markets impose the financial discipline which politicians won’t impose on themselves.

The mini-Budget reaction

A good example of this happened in the UK in 2022 when the government’s mini-Budget was perceived by the markets to be irresponsible, as it was not fully funded.

UK 10-year yields spiked to 4.5% from 3.5% within days, sterling collapsed towards parity with the US dollar and the Bank of England had to intervene as an emergency buyer to calm markets and help pension funds and insurance companies which were caught out by the sudden rise in yields.

The then chancellor Kwasi Kwarteng was gone within weeks, and the Budget was reversed.

Trump’s tariffs and ‘yippy bonds’

A more recent example is related to President Trump’s Liberation Day tariffs announcement in 2025. US 10-year yields jumped from around 3.6% to 4.8% between 4 April and 10 April, prompting Trump to pause reciprocal tariffs for 90 days.

When asked about the bond market reaction Trump said: “They were getting a little bit yippy, you know, they were getting a little bit yippy, a little bit afraid,” before pushing back on the idea that the market had forced his hand.

Trump’s rejection of the vigilante narrative underlines how difficult it is to ascribe causation in markets. Treasury Secretary Scott Bessant was quick to reframe the narrative as bond markets pricing in stronger US growth.

Ed Yardeni himself described it as “bond vigilantes hit another homerun” implying that bond markets had ‘spooked’ the US administration.

China’s implicit threat to sell US treasuries and hedge funds unwinding bets were contributing factors driving prices down and yields up.

Other factors impacting yields

This underscores the difficulty of untangling the many factors which can impact bond yields. The primary drivers are expected economic growth and inflation.

Higher growth can create inflationary pressures within the economy as demand for resources temporarily outstrips supply.

For example, the current boom in semiconductor chip stocks reflects bottlenecks in the memory chip supply chain which is impacting the cost of the AI infrastructure build out and consumer electronics.

As these effects feed through to official inflation numbers, bond investors may be less willing to buy bonds at prevailing yields, which could push up bond yields.

The term premium effect

The term premium is the price for bearing extra risks associated with longer dated bonds. These include reinvestment risk (given interest rates can change a lot over 10 years), uncertainty over inflation and fiscal supply risk (the danger that a government's tax, spending, or borrowing choices will inadvertently damage a country's ability to produce goods and services).

The current cycle of Federal Reserve rate cuts is a good example of the term premium at work. Since September 2024 the Fed has cut interest rates by a cumulative 2.25%, yet the 10-year treasury yield is higher today.

What explains this divergence?

The term premium has been driven by future interest rate expectations, fiscal deficits and rising geopolitical risks.

Ongoing military conflicts in the Middle East have driven oil prices higher which has sparked worries over persistent inflation. The build out of AI infrastructure is also a worry for inflation watchers.

The resilience of the US economy and robust corporate earnings signals that lower long-term borrowing costs are not necessary.

Finally, persistent US budget deficits mean more debt issuance and bond investors have become more price-sensitive in absorbing the supply of government debt.