BCA analysts Matt Gertken and Yushu Ma argue that a democratic socialist movement could eventually create the political appetite for higher taxes, particularly if the national debt forces a reckoning over public finances. But the constraint is already visible in the bond market, where a sell-off in long-term US government debt is pushing borrowing costs higher.
The spread between two-year and 10-year Treasury yields has widened by nearly 29 basis points since 24 June, according to FactSet data. The move has been driven largely by rising 10-year yields, which traded above 4.7% on Tuesday, even as the Federal Reserve has kept its policy rate unchanged.
That matters beyond financial markets. Longer-term Treasury yields influence consumer borrowing costs, including mortgages. A typical 30-year mortgage now costs about 6.75%, adding further pressure to an already difficult housing market.
The contrast with Wall Street is stark. The S&P 500 has returned a cumulative 77% over the past three years, while stock ownership remains concentrated among wealthier Americans. Households with limited exposure to those gains are still exposed to the cost of higher borrowing, fuel and housing.
Several pressures are feeding the rise in yields. The war with Iran has constrained oil flows from the Middle East, while US refineries are operating near capacity. Diesel cost $5.46 a gallon on Tuesday, up 48% from a year earlier, according to AAA data.
At the same time, technology companies are drawing heavily on debt markets to finance AI data centres and related infrastructure. That demand competes with government borrowing for investor capital, while supply bottlenecks in chips and strains on ageing electricity grids add to price pressures.
Robin Brooks of the Brookings Institution has argued that the immediate trigger for the bond-market sell-off is less important than the fiscal weakness underneath it. Large deficits and high debt levels leave governments more vulnerable when shocks arrive.
The Congressional Budget Office expects the US budget deficit to reach about $2.1tn, or 6.4% of GDP, for the fiscal year ending in September. The Trump administration has linked part of the spending increase to the Iran war, but it has not set out a clear path for reducing the deficit.
Federal Reserve chair Kevin Warsh has acknowledged that conditions appear restrictive for households, particularly in housing, while remaining comparatively loose for Wall Street. His acceptance of higher long-term yields as evidence that markets are tightening may have reinforced investors’ willingness to keep selling bonds.
Warsh may offer further signals at the Jackson Hole gathering on 28 August. Yet the Fed cannot directly resolve the imbalance between government spending and revenue. If long-term yields remain elevated, the bond market could become not only a financial constraint but a deeper political one, intensifying public anger over debt, inequality and the cost of living.
