A Monetary-Fiscal Theory of Sudden Inflations
What this paper finds — and why it matters
Overview
Research Question. Why do sudden inflations and currency crises occur, while symmetric sudden deflations never do? The paper asks whether treating nominal government bonds as analogous to ordinary corporate bonds — with an asymmetric payoff structure capped at face value on the upside but exposed to real losses when fiscal surpluses are insufficient — can generate a unified theory of these crises endogenously from a single model.
Intellectual Lineage and Approach. The paper sits at the intersection of two literatures. The first is the Fiscal Theory of the Price Level (FTPL), originating with Leeper (1991), Sims (1994), and Sargent and Wallace (1985), which links the real value of nominal government debt to expected future surpluses. The second is the safe-asset literature, where Holmstrom (2015) and Gorton (2017) explain that assets can circulate as safe stores of value precisely because their backing is costly to investigate and consumers rationally remain uninformed. The paper applies this information-economics logic to nominal government bonds, so that consumers normally hold bonds without investigating the government’s true fiscal capacity, and only pay the cost to investigate when real repayment doubts become sufficiently severe.
Model Structure. The model is a two-period reduced-form general equilibrium. In period 1, a representative consumer buys nominal government bonds at an interest rate set by the monetary authority. In period 2, the government must repay those bonds. The fiscal authority attempts to hit a price-level target P* by raising tax revenue, but faces a hard ceiling τ_max on the surplus it can collect — arising from Laffer limits on taxation, political constraints on austerity, or the need to fund financial-sector bailouts. The consumer has prior beliefs that τ_max is low (L) with probability π and high (H) with probability 1−π, and can pay a fixed utility cost γ to learn τ_max before deciding how many bonds to purchase.
Bond Payoff Structure and Asymmetry. The key mechanism is the asymmetric, bond-like real payoff of nominal government debt. If τ_max ≥ B1/P*, the government raises enough surplus to repay bonds fully in real terms at the price-level target; the real payoff is flat at face value (the “in-the-money” region). If τ_max < B1/P*, the government sets taxes to the ceiling τ_max and the price level rises above P* to balance the budget constraint, reducing the real payoff proportionally (the “default” region). Critically, because the nominal payoff is capped at face value, there is no upside region: governments will not run surpluses large enough to deliver a windfall to bondholders, so sudden deflations — analogous to a corporate bond being worth more than face value — cannot occur. This asymmetry is the direct source of the one-sided nature of crises.
Two Illustrative Mechanisms for Sudden Inflations. The paper numerically and analytically characterizes two triggering scenarios:
Lower surplus expectations (fiscal stress narrative, corresponding to Burnside et al. 2001 on the 1997 Asian crisis): As the probability π of a low future surplus (e.g., from a prospective banking-sector bailout) rises, the value of information about τ_max increases. In the numerical example (i = 0.05, γ = 0.13, L = 0.1), the value of information equals the cost γ at π = 0.15. For π above 0.15, consumers pay to investigate, learn τ_max = L, and refuse to purchase bonds beyond what will be repaid in real terms (B1 = τ_max = L = 0.1). The price level in period 1 rises discontinuously as a function of π at this threshold.
Interest rate increases (speculative attack narrative): As the monetary authority raises the interest rate to defend a currency, consumers demand more bonds. Larger bond quantities increase the risk that surpluses will be insufficient, raising the value of fiscal information. In the numerical example (π = 0.5, γ = 0.24, 1+i ∈ [1, 1.2]), the value of information equals γ at 1+i = 1.1 (i.e., i = 10%). For interest rates above this threshold, consumers learn τ_max = L, restrict bond purchases to what will be repaid, and the price level in period 1 jumps discontinuously. Further interest rate increases above the threshold produce only upward drift in the price level, not additional monetary tightening effects — illustrating the limits of monetary policy in fiscally stressed environments.
Theoretical Results. Two formal theorems establish generality. Theorem 1 shows that, given bond demand B1(π) such that L < B1 for all π ∈ (0,1), there exist thresholds k and γ > 0 such that the period-1 price level P1 is discontinuous as a function of π on (0, k]. Theorem 2 establishes an analogous discontinuity in P1 as a function of the interest rate i, given that B1(i) > L for all i in the relevant range.
Scope Conditions. The model is a two-period reduced form that abstracts from dynamics, multiple maturities, and secondary market trading. The informational friction is a fixed binary cost γ, not a richer signal structure. The results depend on the existence of a binding surplus ceiling τ_max; when the government is far from this ceiling (i.e., consumers’ beliefs are far from the “default boundary”), shocks produce only small, smooth price-level changes. Large discontinuous price-level jumps require the economy to be near the kink point of the bond payoff curve.
Q&A
Q1: What is the fundamental analogy that drives the paper’s theory, and what economic literature does it build on?
The paper analogizes nominal government bonds to corporate bonds (following Sargent 1982’s advice that “government debt is valued according to the same economic considerations that give private debt value”). Like a corporate bond, the nominal government bond pays its face value if the underlying project (government fiscal capacity) delivers a surplus at least equal to the face value, but pays only a share of the realized surplus if the surplus falls short. This bond-like payoff — flat on the upside, proportional to outcomes on the downside — is the direct source of asymmetric crisis dynamics. The paper combines this with Holmstrom (2015) and Gorton (2017)’s framework in which safe assets function because their backing is costly to investigate, so consumers rationally remain uninformed in normal times.
Q2: What is the key information friction, and how does it generate the switch between “normal times” and crisis?
In normal times, consumers are confident that the government’s future maximum surplus τ_max is sufficient to repay bonds in real terms. The fixed utility cost γ of investigating the true surplus exceeds the benefit, so consumers remain uninformed and bonds trade at a price reflecting only uninformed prior beliefs. A crisis arises when the value of information V(.) rises above γ — either because the probability of a low surplus state rises (fiscal stress) or because the interest rate rises and consumers demand more bonds, bringing them closer to the repayment boundary. Once V > γ, consumers investigate and, upon learning τ_max = L (low surplus), refuse to hold bonds that will not be repaid in real terms, triggering a discrete upward jump in the price level.
Q3: How does the bond payoff structure explain the absence of sudden deflations?
The real payoff of a nominal government bond cannot exceed its face value: the bond is capped at face value on the upside because the government will not voluntarily raise tax surpluses to deliver a windfall to bondholders. In the event that surpluses turn out to be higher than needed (τ_max ≥ B1/P*), the government simply sets taxes to exactly repay the bonds at P* and returns no additional real value to bondholders. This is the flat portion of the payoff curve. Because there is no upside kink — no region where learning that τ_max is unexpectedly large causes the price level to fall sharply — there is no mechanism for sudden deflations symmetric to sudden inflations. The 1933 U.S. episode (Jacobson et al. 2019) is cited: when deflation from leaving gold would have required fiscal austerity for full real repayment, Roosevelt chose to exit the gold standard rather than allow deflation.
Q4: How does the first numerical example (lower surplus expectations) work quantitatively?
The baseline parameters are: i = 0.05, γ = 0.13, L = 0.1, H ≈ ∞, P* = 1, e1 = e2 = 1, B0 = 1, τ1 = 0.8, β = 1. The analysis is restricted to π ∈ (0, 0.3]. As π (probability that τ_max = L) rises, the value of information V(.) rises. At π = 0.15, V equals the cost γ = 0.13. For π > 0.15, consumers pay to investigate and, upon learning τ_max = L, purchase only B1 = L = 0.1 in bonds — the amount that will be repaid — causing the period-1 price level P1 to jump discontinuously from approximately 0.95 to approximately 1.13. For π ≤ 0.15, consumers remain uninformed and P1 rises only smoothly from below 1 as π increases (fewer bonds demanded as repayment risk rises, even without investigation).
Q5: How does the second numerical example (interest rate increase) work quantitatively, and what does it imply for monetary policy?
With π = 0.5, γ = 0.24, and 1+i ∈ [1, 1.2], as the monetary authority raises the interest rate, consumers demand more bonds, increasing real repayment risk and the value of information. At 1+i = 1.1 (i.e., i = 10%), V equals γ. For 1+i > 1.1, consumers investigate and learn τ_max = L; they then only purchase bonds up to the repayment limit, causing P1 to jump discontinuously to approximately 1.15. For interest rates above the threshold, further increases yield only a smooth upward slope in P1 (bond purchases are fixed in real amount but nominal revenue falls). This illustrates that the monetary authority’s ability to use higher interest rates to lower the price level is limited by the surplus constraint: once the interest rate is high enough to trigger consumer investigation and a fiscal crisis, raising rates further is inflationary rather than deflationary.
Q6: What are the two regions of the deterministic model and how do they differ in fiscal and price-level dynamics?
In the deterministic version (1-π = 0, so τ_max = L with certainty, and there is no uncertainty), the model produces two distinct regions. In the “insufficient surplus” region where τ_max < B1/P*, the fiscal authority sets taxes to their maximum τ_max, the real payoff of bonds is τ_max/B1 < 1, the period-1 price level P1 = B0/(βτ_max), and real bond revenue Π = βτ_max (constant in τ_max). Selling additional bonds does not raise additional real revenue because any extra bonds lead to a proportional rise in P2 and a fall in Q. In the “sufficient surplus” region where τ_max ≥ B1/P*, the government meets its fiscal target (τ2 = B1/P*), P2 = P* is hit, P1 = βB1/(B0P*), and Π = βB1/P* (increasing in B1). In this region, selling additional bonds does raise real revenue and lowers P1 as the government absorbs more money.
Q7: What are the two interest rate regions in the deterministic model, and what is their implication for monetary policy effectiveness?
Using B1 = B0(1+i) (debt rolled over at the chosen rate), the monetary authority has two interest-rate regions. In the “constrained” region where 1+i > τ_max P*/B0 (the surplus ceiling binds), raising i does not change the period-2 surplus (τ2 = τ_max), does not change real revenue (Π = βτ_max), and does not affect P1 — but raises P2 above the target P*. In the “unconstrained” region where 1+i ≤ τ_max P*/B0, raising i increases bond demand, increases real surplus backing, raises real revenue, and lowers P1 while P2 = P* is maintained. The boundary between these regions determines the limit of monetary policy: the monetary authority can reduce P1 by raising i only up to the point where the surplus ceiling would be hit.
Q8: How does the paper relate to and extend prior FTPL literature?
The paper is grounded in the FTPL of Leeper (1991), Sims (1994), and Cochrane (2005, 2020), in which the price level is determined by the requirement that real government liabilities equal the present value of future surpluses. The paper’s contribution is to make the information structure endogenous: consumers’ beliefs and their decision to acquire fiscal information determine whether or not the FTPL logic is operative. In normal times (consumers uninformed), the price level does not respond to changes in the maximum surplus — a result that resembles the “Ricardian” or non-FTPL regime. When consumers investigate and learn the surplus is insufficient, the connection between the surplus and the price level is restored, reproducing FTPL-type dynamics. This provides an endogenous, single-model rationale for the regime-switching behavior between FTPL and non-FTPL environments documented empirically in Bianchi and Melosi (2013, 2017) and Davig and Leeper (2006).
Q9: What is the welfare role of consumer ignorance in this framework?
Consumer ignorance of the government’s true surplus plays a dual role. On one hand, ignorance is individually rational in normal times because the cost γ of investigating exceeds the benefit V (.) when beliefs are comfortably away from the default boundary. On the other hand, following Dang et al. (2017), informed knowledge of the safe asset’s backing destroys the symmetric ignorance that supports the asset’s role as a safe store of value, reducing welfare. In this model the concern is repayment risk rather than adverse selection: the consumer fears not being repaid in real terms and chooses to investigate when that risk is sufficiently high, potentially triggering the very crisis they feared.
Q10: What are the scope conditions and limitations of the model?
The model is explicitly a two-period reduced form designed to illustrate the bond-payoff mechanism in the simplest possible setting. It abstracts from: multi-period bond maturities and secondary market trading; rich heterogeneity among consumers; endogenous monetary and fiscal policy responses beyond the simple rules specified; and the general equilibrium interactions between inflation, output, and labor markets. The information cost γ is modeled as a fixed binary cost rather than a continuous or richer signal structure. The results on discontinuous price-level jumps hold when bond demand is sufficiently large relative to L (i.e., L < B1), ensuring genuine repayment risk; when surpluses are very large relative to bond liabilities, no crisis dynamics arise.
Key Concepts
Maximum Surplus (τ_max). The paper’s name for the hard ceiling on the net tax revenue (taxes minus money transfers) the government can collect in the second period. This ceiling can arise from a Laffer limit on taxable income, political-economy constraints on austerity, or from a banking crisis requiring government transfers to bail out the financial sector. It is the paper’s analogue of a project’s liquidation value: the maximum the “project” (the government) can deliver to bondholders.
Bond-Like Payoff of Nominal Government Debt. The paper’s central structural claim: the real payoff to holding a nominal government bond is capped at face value on the upside (the government will not raise surpluses beyond what is needed to repay bonds at the price-level target) but falls proportionally below face value when τ_max is insufficient for full real repayment. This is precisely the payoff structure of a standard corporate bond — flat on the upside, proportional to recovery on the downside — and it is the source of the asymmetry between sudden inflations and the absence of sudden deflations.
Value of Information (V(.)). Defined as the difference in expected utility between a consumer who learns the true τ_max before making bond-purchase decisions and one who remains uninformed and acts only on prior beliefs π, 1−π. The consumer investigates if and only if V(.) > γ. V is zero when beliefs are certain (limπ→0 and limπ→1), can be hump-shaped in π, and is increasing in the interest rate i (through its effect on bond demand). The threshold condition V = γ defines the boundary between “normal times” (no investigation) and crisis (investigation and possible sudden inflation).
Endogenous Information Structure. The paper’s term for the property that whether consumers choose to learn the government’s fiscal capacity is itself determined within the model by the parameters of the economy (the interest rate, prior beliefs, the cost of investigation). This contrasts with models that exogenously specify whether agents are informed or not. The endogenous information structure is the mechanism by which the paper generates the two apparent regimes (FTPL-active vs. FTPL-dormant) from a single unified model.
Default Boundary. The kink point in the bond payoff curve at τ_max = B1/P*: the level of the maximum surplus at which the government exactly repays bonds in real terms at the price-level target. When beliefs or bond quantities place the economy near the default boundary, small changes in π or i can push the economy across it, triggering large price-level responses. When the economy is far from the boundary (τ_max comfortably above B1/P*), small shocks have only small smooth effects.
Sudden Inflation / Currency Crisis (as defined in this paper). A discrete, discontinuous jump in the period-1 price level P1 that occurs when consumers pass the threshold V(.) = γ and investigate the government’s fiscal capacity, finding surpluses to be insufficient. The mechanism is: informed consumers refuse to hold bonds they know will not be repaid in real terms at P*, forcing the price level to jump to clear the government’s budget constraint with fewer bonds outstanding. The paper treats sudden inflations and currency crises as the same mechanism in different institutional contexts.
Repayment Risk Premium. The markup above the risk-free rate that consumers require on government bonds to compensate for the probability that the government’s surplus will be insufficient for full real repayment (i.e., the probability that the economy is in the τ_max < B1/P* region). This premium is present even when consumers are uninformed (i.e., do not know which state of τ_max will occur), and is reflected in the consumer’s first-order condition for bond demand.