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Financial support from National Science Foundation Grant No. SES-1559209 is gratefully acknowledged. We introduce a new class of solutions to nonlinear forward-looking models called near-rational sunspot equilibria (NRSE). NRSE are natural nonlinear extensions of the usual sunspot equilibria associated with the linearized version of the economy, and are near-rational in that agents use the optimal linear forecasting model when forming expectations. Generic results for existence and stability under learning are established. NRSE in indeterminate nonlinear models are found to be stable under learning provided that the corresponding linearized model's minimal state variable solution is E-stable. NRSE are readily computable, and our results make it possible to use the standard linear tools to search for stable NRSE. We illustrate our results using a canonical nonlinear New Keynesian model. Postprint

International audience; In this paper we investigate if government balanced-budget rules together with endogenous taxation may lead to aggregate instability in an endogenous growth framework. After highlighting the differences with the exogenous growth framework, we prove that under counter-cyclical consumption taxes, while there exists a unique balanced growth path, sunspot equilibria based on self-fulfilling expectations occur through a form of global indeterminacy. In addition, we argue that this result is empirically plausible for a large set of OECD countries and that it may also emerge with endogenous income taxes.

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We present an experiment in which extrinsic information (signals) may generate sunspot equilibria. The underlying coordination game has a unique symmetric non-sunspot equilibrium, which is also risk-dominant. Other equilibria can be ordered according to risk dominance. We compare treatments with different salient, but extrinsic signals. By increasing the precision of private signals, we manipulate the available public information, which allows us to measure the force of extrinsic signals. We also vary the number of signals and combine public and private signals, allowing us to see how subjects aggregate available (and possibly irrelevant) information. Results indicate that sunspot equilibria emerge naturally if there are salient (but extrinsic) public signals. However, salient private signals of high precision may also cause sunspot-driven behavior, even though this is no equilibrium. The higher the precision of signals and the easier they can be aggregated, the more powerful they are in dragging behavior away from the risk-dominant to risk-dominated strategies. Sunspot-driven behavior may lead to welfare losses and exert negative externalities on agents, who do not receive extrinsic signals.

We study optimal monetary and fiscal policy in a New Keynesian model where occasional declines in agents' confidence can give rise to persistent liquidity trap episodes. Unlike in the case of fundamental-driven liquidity traps, there is no straightforward recipe for mitigating the welfare costs and the systematic in ation shortfall associated with expectations-driven liquidity traps. Raising the in ation target or appointing an in ation-conservative central banker improves in ation outcomes away from the lower bound but exacerbates the shortfall at the lower bound. Using government spending as an additional policy tool worsens stabilization outcomes both at and away from the lower bound. However, appointing a policymaker who is sufficiently less concerned with government spending stabilization than society can eliminate expectations-driven liquidity traps altogether.

Summary.: We show that for international economies with two countries, in which agents have additively separable utility functions, the existence of sunspot equilibria is equivalent to the occurrence of the transfer paradox. This equivalence enables us to provide some new insights on the relation of the existence of sunspot equilibria and the multiplicity of spot market equilibria

I consider the set of equilibria of two-period economies with S extrinsic states of nature in the second period and I assets with linearly independent nominal payoffs. Asset prices are variable. If the number of agents is greater than (S-I), the payoff matrix is in general position and S \(\ge\) 2I, the set of equilibrium allocations generically (in utility function space) contains a smooth manifold of dimension (S-1). Moreover, the map from states o f nature to equilibrium allocations (restricted to this manifold) is one-to-one at each equilibrium.

Economies with oligopolistic markets are prone to inefficient sunspot fluctuations triggered by autonomous changes in firms equilibrium conjectures. We show that a well designed taxation-subsidization scheme can eliminate these fluctuations by coordinating firms in each sector on a single efficient equilibrium. At the macroeconomic level, implementing this stabilization policy leads to significant welfare gains, attributable to a quantitatively dominant "efficient stabilization effect". This effect, while important, is typically ignored in the traditional computations of the welfare costs of aggregate fluctuations (e.g., Lucas, 2003).

We consider a two-sector economy with money-in-the-utility-function and sector-specific externalities. We provide conditions on technologies leading to the existence of local indeterminacy for any value of the interest rate elasticity of money demand, provided the elasticity of intertemporal substitution in consumption is large enough. Moreover, we show that the occurrence of multiple equilibria is intimately linked with the existence of a flip bifurcation and period-two cycles.

In this paper, we study the occurrence of local indeterminacy in two-sector monetary economies. In order to capture the credit market imperfections and the liquidity services of money, we consider a general MIUF model with two alternative timings in monetary payments: the Cash-In-Advance timing, in which the cash available to buy goods is money in the consumers' hands after they leave the bond market but before they enter the goods market, and the Cash-After-the-Market timing, in which agents hold money for transactions after leaving the goods market. We consider three standard specifications of preferences: the additively separable formulation, the Greenwood-Hercovitz-Huffman (GHH) [18] formulation and the King-Plosser-Rebelo (KPR) [21] formulation. First, we show that for all the three types of preferences, local indeterminacy easily arises under the CIA timing with a low enough interest rate elasticity of money demand. Second, we show that with the CAM timing, determinacy always holds under separable preferences, but local indeterminacy can arise in the case of GHH and KPR preferences. We thus prove that compared to aggregate models, two-sector models provide new rooms for local indeterminacy when non-separable standard preferences are considered.

In the present paper stationary pure-exchange overlapping generations economies with L goods per date and M consumers per generation are considered. It is shown that for an open and dense set of utility functions there exist endowment vectors such that N-cycles exist for N less than or equal to L+1 and L less than or equal to M. The approach to existence of endogenous fluctuations is basic in the sense that the prime ingredients are the implicit function theorem and linear algebra. Moreover it is sketched how the approach can be applied to show that for an open and dense set of utility functions there exist endowment vectors such that sunspot equilibria, where prices at every date only depends on the state at that date, exist.

In dynamic economic models derived from optimization principles, the forward equilibrium dynamics may not be uniquely defined, while the backward dynamics is well defined. We derive properties of the global forward equilibrium paths based on properties of the backward dynamics. We propose the framework of iterated function systems (IFSs) to describe the set of forward equilibria and apply the IFS framework to a one- and a two-dimensional version of the overlapping generations (OLG)-model. We show that if the backward dynamics is chaotic and has a homoclinic orbit (a "snap-back repeller"), the set of forward equilibrium paths converges to a fractal attractor. Forward equilibria may be interpreted as sunspot equilibria, where a random sunspot sequence determines equilibrium selection at each date.Keywords: Forward and backward dynamics; Chaos; Homoclinic orbit; Snap-back repellor; Sunspot equilibria; Overlapping generations modelsJEL classification codes: E32; C62; C02

We introduce a solution technique for the study of discrete time stochastic models populated by long-lived agents. We introduce aggregate uncertainty and complete markets into a 'perpetual-youth' model of a kind first studied by Olivier Blanchard and we show that the pure-trade version of the model behaves much like the two-period overlapping generations model. Our methods are easily generalized to economies with production and they should prove useful to researchers who seek a tractable stochastic model in which fiscal policy has real effects on aggregate allocations.

In this paper, is show how procyclical capital flows originate boom-bust and sunspot episodes in a neoclassical growth model of a small, open economy. All markets are perfect, with the exception of the fact that some upper, endogenous limit is imposed on how much the economy can borrow from foreign creditors, due to potential debtor default. It is shown that the steady state is locally indeterminate when the credit multiplier is larger than some threshold level, whereas saddle-point stability prevails when the credit multiplier is low enough. As a consequence, high levels of the credit multiplier lead to both booms followed by busts and sunspot-driven volatility near the steady state, while, in contrast, low levels ensure monotonic convergence. Compared with saddle-path equilibria, boom-bust and sunspot equilibria are associated with both lower welfare and debt overhang, that is, a crowding-out effect of credit : when the economy is highly leveraged, it uses savings to cut down foreign debt, at the expense of both human and physical investment. Numerical examples show that volatility arises at rather low values of financial development and for debt-to-GDP ratios that fall within the range of available estimates. Finally, the effects of shocks to the world interest rate on output and consumption are amplified and persistent in the debt overhang regime.

We consider a two‐sector infinite horizon economy with a fractional cash‐in‐advance constraint on consumption expenditures. This formulation allows us to consider a steady‐state velocity of money that is strictly greater than one and, therefore, provides a more plausible framework than the standard formulation in which all the consumption purchases are paid cash. We prove that the steady state is bound to be indeterminate and multiple equilibria occur when the share of the liquidity constraint is low enough and that a capital‐intensive investment good or a strongly capital‐intensive consumption good improve considerably the scope for indeterminacy. As a consequence, we show that without any restriction on the elasticity of intertemporal substitution in consumption, multiple equilibria might occur if the velocity of money is greater than a critical bound that is compatible with empirical estimates.

We consider economies with additively separable utility functions and give conditions for the two-agents case under which the existence of sunspot equilibria is equivalent to the occurrence of the transfer paradox. This equivalence enables us to show that sunspots cannot matter if the initial economy has a unique spot market equilibrium and there are only two commodities or if the economy has a unique equilibrium for all distributions of endowments induced by asset trade. For more than two agents the equivalence breaks and we give an example for sunspot equilibria even though the economy has a unique equilibrium for all distributions of endowments induced by asset trade.

In this paper we build a model of financial intermediation that explains the pattern of GDP variability in an economy during the development process. We find evidence that per capita output is more volatile in middle-income economies than in both low and high-income economies. We show that, if the model economy is in the early or in the mature stages of development, there is a unique equilibrium. However, in the middle stages of development, multiple equilibria exist. Moreover, we find that in economies with imperfect credit markets, per capita output volatility tends to be higher than in economies with perfect or non-existent credit markets.

International audience; It is well known from the literature that the introduction of liquidity constraints in infinite-horizon economies may be responsible for the occurrence of local indeterminacy and sunspot fluctuations. Yet, the question of the robustness of such phenomena when the constraints are progressively relaxed, and the possibility of intertemporal arbitrage on the part of the agents increases, remains open. In this paper we study such an issue by departing from the Cazzavillan et al. (J. Economic Theory 80 (1998) 60-107) framework with heterogeneous agents, financial constraint on wage income, and positive externalities in aggregate capital and labor. We observe that local indeterminacy and sunspot fluctuations persist for a wide range of amplitudes of the liquidity constraint, although they finally disappear when the 'degree' of liquidity of the economy is made arbitrarily large. © 2002 Elsevier Science B.V. All rights reserved.