Why rise in government debt is freaking out bond market

Australia's government now needs to offer investors over 5% on its 10-year bonds, reaching a 15-year high after a long period of low rates since the 2008 financial crisis. U.S. 10-year rates sit around 4.7%, up nearly half a percent this year, while the 30-year bond approaches a two-decade peak. The UK also saw 10-year bond rates hit a 15-year high.

Higher rates mean higher interest payments for governments, limiting their ability to spend or cut taxes. This applies to both the federal government and state governments, with Victoria's 10-year bonds now paying 5.55% interest.

Market interest rates are driven by supply and demand. Governments issue bonds to finance spending not covered by tax revenue. Bond issuances come from households (mortgages), businesses (operations funding), and governments (often due to past budget deficits).

The largest driver is government debt. Larger debt means more bonds must be issued, raising interest rates needed to attract investors. U.S. national debt has grown to over $40 trillion, nearly 20 times Australia's entire economy, while Australia's federal debt recently surpassed $1 trillion.

Central banks manage short-term interest rates through the cash market, using the cash rate to influence borrowing demand. Raising rates slows economic demand and reduces inflation. However, they can't directly control long-term interest rates like 10-year bonds, which fluctuate based on investor demand.

The U.S. has enjoyed a unique position in global markets, issuing growing volumes of bonds without needing to offer higher rates. This "exorbitant privilege" stems from the U.S. dollar's dominance in global trade and financial transactions. Attempts by U.S. Treasury Secretary Scott Bessent to shrink supply and lower rates have had little impact, as investors see increasing U.S. government financing needs, inflation fears, and corporate bond issuance fueling higher rates.