The fiscal theory of the price level (FTPL) and the quantity-theory (monetarist) account are the two leading theoretical explanations of how the general price level is determined in a fiat-money economy. Despite forty years of literature, there is still no consensus on what, precisely, distinguishes them: candidate defining characteristics include determinacy of rational-expectations equilibria under interest-rate targets versus price-level paths driven by the government bond stock and diverging from the nominal money stock. This unresolved definitional ambiguity feeds a sharper scientific question: do the two theories have distinct observable implications at all — and if so, what evidence (statistical identification restrictions, policy experiments, or direct information about the policy process) could determine which theory governs price-level determination in a given economy? The problem remains open: the literature, from Buiter's (2002) critique through the most recent work (2020–2026), spans mutually incompatible positions — FTPL as an incoherent relabeling, as observationally equivalent by construction, as one complementary pillar among several, or as a third 'central-bank' theory — and no accepted empirical identification strategy exists.

Background

In a fiat-money economy the general price level PP is the rate at which nominal objects (currency, reserves, government bonds) convert into goods. Two broad theories explain what pins down PP. The quantity theory of money — the core of monetarism — holds that PP is determined by the nominal stock of money via the relation MV=PYMV = PY (money stock times velocity equals nominal output): with stable money demand, the money supply drives the price level, so inflation is ultimately a monetary phenomenon under the central bank's control. The fiscal theory of the price level (FTPL), developed from Leeper's (1991) regime taxonomy and Sargent and Wallace's (1981) 'unpleasant monetarist arithmetic' (the result that a fiscal authority that refuses to adjust taxes can force the central bank to inflate away debt), and articulated by Sims (1994) and Woodford, instead starts from the government's intertemporal budget constraint: the real value of outstanding nominal government debt must equal the present value of real primary surpluses (government revenue minus non-interest spending). In a Ricardian fiscal regime, taxes always adjust to validate any price level, so this equation is a constraint that disciplines fiscal policy; in a non-Ricardian (fiscally dominant) regime, the equation becomes a valuation equation that determines PP: if surpluses do not adjust, the price level jumps so that inflation revalues the debt. A central bank pursuing an interest-rate target (a Taylor rule, i.e. a nominal interest-rate path that responds systematically to inflation) then determines expected inflation, while news about the present value of surpluses drives unexpected inflation. Two families of policy regimes are conventionally distinguished (Leeper 1991): 'active/passive' monetary/fiscal mixes, in which exactly one authority systematically reacts to stabilize debt.

Against this background, McCallum and Nelson (2006) documented that the field does not even agree on what the FTPL's defining characteristic is: some proponents emphasize its implications for interest-rate pegging and determinacy of rational-expectations (RE) equilibria (whether the model pins down a unique equilibrium price path), others its capacity to generate equilibria in which the price level tracks the stock of government bonds and diverges drastically from the nominal money stock. McCallum and Nelson concluded that the two theories differ 'irreconcilably' only under money-stock policy rules, that they differ more subtly (over the monetary-accommodation process) under interest-rate rules, and that adaptive-learning (learnability) criteria — which ask which equilibria are stable under plausible boundedly-rational updating, and hence more plausible — tend to favor the monetarist equilibrium. Gordon and Leeper (2006) took the opposite view, following Hicks in calling the dispute over whether the price level is set 'in the money market' or 'in the bond market' a sham: in their portfolio-balance framework both the quantity theory and the FTPL are special cases of joint monetary-fiscal determination, and monetary and fiscal adjustments can jointly generate identical price-level changes — an 'attribution ambiguity'. Cochrane (2011) showed that in the new-Keynesian framework (the standard sticky-price RE model of the business cycle) with a Taylor rule, Taylor-rule parameters are not identified in the determinate equilibrium, and noted that what determines the price level in a modern fiat-money economy with an interest-rate-targeting central bank remains without a fully accepted, empirically supported theory — with the FTPL the leading candidate but its empirical identification unresolved. The question matters practically: whether a central bank can control inflation independently of fiscal policy, and whether monetary-fiscal coordination is necessary for price stability, hinge on which theory is right and on whether the data can tell the regimes apart.

Problem Statement

The problem, in its natural generality, is to determine whether the fiscal theory of the price level and the monetary (quantity-theory) theory of the price level are genuinely distinct theories of price-level determination, and if so, how they can be told apart. Concretely, it asks: (i) Definitional core — is there a precise, agreed characterization of what distinguishes the fiscal theory from the monetarist account (e.g., determinacy of rational-expectations equilibria under interest-rate targets versus bond-stock-driven price levels diverging from the nominal money stock, the treatment of the government intertemporal budget constraint as a valuation equation versus a constraint, or the source of the nominal anchor — the variable or institution that ultimately pins down the price level), resolving the documented disagreement over the FTPL's defining characteristic? (ii) Observable core — do the two theories have distinct observable implications: under what conditions (model classes, policy-rule families, frictions) are they observationally equivalent versus distinguishable, and what specific evidence — testable identification restrictions in time-series data, contrasts in the effects of money-for-debt exchanges versus unfunded transfers, or direct information about the policy process — could determine which theory governs price-level determination in an actual economy?

References

  1. Bennett T. McCallum and Edward Nelson (2006), 'Monetary and Fiscal Theories of the Price Level: The Irreconcilable Differences', NBER Working Paper 12089. DOI 10.3386/w12089. https://www.nber.org/papers/w12089
  2. David B. Gordon and Eric M. Leeper (2006), 'The Price Level, the Quantity Theory of Money, and the Fiscal Theory of the Price Level', Scottish Journal of Political Economy 53(1):4–27. DOI 10.1111/j.1467-9485.2006.00368.x. https://doi.org/10.1111/j.1467-9485.2006.00368.x
  3. John H. Cochrane (2011), 'Determinacy and Identification with Taylor Rules', Journal of Political Economy 119(3):565–615. DOI 10.1086/660817. https://doi.org/10.1086/660817
  4. Eric M. Leeper (1991), 'Equilibria under "active" and "passive" monetary and fiscal policies', Journal of Monetary Economics 27(1):129–147. DOI 10.1016/0304-3932(91)90007-B. https://doi.org/10.1016/0304-3932(91)90007-B
  5. Thomas J. Sargent and Neil Wallace (1981), 'Some Unpleasant Monetarist Arithmetic', Federal Reserve Bank of Minneapolis Quarterly Review (reprinted 1985, 9(1)). DOI 10.21034/qr.913. https://doi.org/10.21034/qr.913
  6. Christopher A. Sims (1994), 'A simple model for study of the determination of the price level and the interaction of monetary and fiscal policy', Economic Theory 4(3):381–399. DOI 10.1007/BF01215378. https://doi.org/10.1007/BF01215378
  7. Willem H. Buiter (2002), 'The Fiscal Theory of the Price Level: A Critique', The Economic Journal 112(481):459–480. DOI 10.1111/1468-0297.00726. https://doi.org/10.1111/1468-0297.00726
  8. John H. Cochrane (2022), 'Fiscal Histories', Journal of Economic Perspectives 36(4):125–146. DOI 10.1257/jep.36.4.125. https://doi.org/10.1257/jep.36.4.125
  9. Pierpaolo Benigno (2020), 'A Central Bank Theory of Price Level Determination', American Economic Journal: Macroeconomics 12(3):258–283. DOI 10.1257/mac.20190008. https://doi.org/10.1257/mac.20190008
  10. John H. Cochrane (2023), 'The Fiscal Theory of the Price Level', Princeton University Press (Chapter 22, 'Observational Equivalence', DOI 10.1515/9780691243245-025). DOI 10.2307/j.ctv2sbm8kh. https://doi.org/10.2307/j.ctv2sbm8kh
  11. Jean Barthélemy, Eric Mengus and Guillaume Plantin (2024), 'The central bank, the treasury, or the market: Which one determines the price level?', Journal of Economic Theory 220:105885. DOI 10.1016/j.jet.2024.105885. https://doi.org/10.1016/j.jet.2024.105885
  12. John H. Cochrane (2025), 'Monetary-Fiscal Interactions', NBER Working Paper 34257. DOI 10.3386/w34257. https://www.nber.org/papers/w34257
  13. Laura Castillo-Martinez and Ricardo Reis (2026), 'How Do Central Banks Control Inflation? A Guide for the Perplexed', Journal of Economic Literature 64(1):195–245. DOI 10.1257/jel.20251429. https://doi.org/10.1257/jel.20251429