Beware the Bubble — in the Bond Market

The question comes up whenever anyone knowledgeable is asked about the markets: Are we in a bubble? It is almost always about the stock market, which has reached record levels lately despite all the unsettling news. Hardly anyone ever asks about the bond market — but a bond bubble could be far more dangerous than an equity bubble.

It may seem an odd moment for this question, given that nominal yields on 10-year US Treasury bonds topped 4.3% last week. That’s high relative to recent history, but it’s low considering another government figure released last week: 100.2%, which is the US debt-to-GDP ratio as of March 31. That means America’s public debt is now greater than the size of its economy. The debt-to-GDP ratio is expected to reach 107% by 2030, exceeding the postwar high of 106% in 1946.

And yet, while rates have been elevated since inflation returned and sometimes go up with news of tariffs or higher oil prices, a yield of 4.3% amounts to about 2% after expected inflation. In other words: This is not a market worried about debt. And to be fair, people have been sounding these warnings for years (ahem, myself included) and nothing has happened. Debt has gone up and yields have gone down.

rising debt

One reason that yields aren’t higher may be that markets expect more rate cuts this year, especially with Kevin Warsh taking over as chair of the Federal Reserve. Or maybe bond markets, like stock markets, have AI fever. There is an argument that AI will transform the economy and increase government revenue faster than the government can increase spending, which will reduce the debt and cause rates to fall.