The Moody’s announcement sent the yield on a 30-year Treasury bond to a high of 5.01% at one point on Monday. Bond yields rise as bond prices fall. When a selloff hits and demand for bonds dries up, it sends bond prices lower. In turn, bond yields move higher.

For most sovereigns, the two debt burden metrics and the two debt affordability metrics are equally weighted. But because the US is a reserve currency issuer, Moody’s tweaks the weights on its scorecard so that the Debt Burden sub-factors each attract a 5 per cent weight, and each Debt Affordability sub-factor attracts a 45 per cent weight.