A small empirical literature (e.g. Canzoneri, Cumby, and Diba 2001, Cochrane 2001) has
looked into the usefulness of (2) in accounting for the evolution of prices. The results are not very favorable; in particular, when a government runs an unexpected deficit, the real market price of its debt increases, suggesting that households expect that the government will make up for the shortfall through increased surpluses in the future. If future surpluses were exogenous and fixed, (2) would suggest that an unexpected deficit should have its primary effect through inflation, by depressing the real market value of debt. While these observations cannot refute the central claim of the FTPL, that (2) is only an equilibrium condition, they call into question the usefulness of the FTPL to explain actual inflationary episodes.