How does faster productivity growth raise the value of government debt?
Core argument: The authors find U.S. government debt has a large positive productivity beta, because the tax code makes revenue highly sensitive to productivity growth as households creep into higher tax brackets while spending commitments barely change in the short run.
We find that U.S. government debt has a large positive productivity beta: its fundamental value seems highly sensitive to the long-run productivity growth outlook. [Given] the tax code, government revenue is highly sensitive to productivity growth while its spending is not. When the economy grows faster, the government collects more tax revenue, as households creep into higher tax brackets, but its spending commitments barely change in the short run. Bondholders are long in a levered claim to GDP and short in a portfolio of inflation-indexed bonds. This means that bondholders are implicitly long productivity growth: they benefit when growth surprises to the upside, and they suffer when growth disappoints. As a result, if investors revise their estimate of productivity growth upwards, they should mark up their valuation of government debt, even if they anticipate higher real rates. If the market became more confident that AI would deliver sustained productivity gains, the repricing of government debt could be substantial. Nominal yields would decline because investors expect inflation to be lower, as predicted by the fiscal theory of the price level. In addition, the supply of Treasurys would decline as well, which would put upward pressure on the convenience yields on Treasurys. Finally, the nominal term premium would likely compress as the government’s fiscal position improves, reducing the risk of higher inflation in bad states of the world.






