Working papers results

We propose to bring together two conceptually complementary ideas: (1) selfconfirming equilibrium (SCE): at rest points of learning dynamics in a game played recurrently, agents best respond to confirmed beliefs, i.e., beliefs consistent with the evidence they accumulated, and (2) ambiguity aversion: agents, other things being equal, prefer to bet on events with known rather than unknown probabilities and, more generally, distinguish objective from subjective uncertainty, a behavioral trait captured by their ambiguity attitudes. Using as a workhorse the 'smooth ambiguity' model of Klibanoff, Marinacci and Mukerji (2005), we provide a definition of 'Smooth SCE' which generalizes the traditional concept of Fudenberg and Levine (1993a,b), here called Bayesian SCE, and admits Waldean (maxmin) SCE as a limit case. We show that the set of equilibria expands as ambiguity aversion increases. The intuition is simple: by playing the same strategy in a stable state an agent learns the implied objective probabilities of payoffs, but alternative strategies yield payoffs with unknown probabilities; keeping beliefs fixed, increased aversion to ambiguity makes such strategies less appealing. In sum, by combining the SCE and ambiguity aversion ideas a kind of 'status quo bias' emerges: in the long run, the uncertainty related to tested strategies disappears, but the uncertainty implied by the untested ones does not. We rely on this core intuition to show that different notions of equilibrium are nested in a simple way, from finer to coarser: Nash, Bayesian SCE, Smooth SCE and Waldean SCE. We also prove some equivalence results under special assumptions about the information structure.

The current account has always been a neglected variable in the management of the Euro area and in the assessment of its members' performance; so has, as a consequence, the savings-investment balance. This paper first reviews the arguments that explain this attitude and justify, under some conditions and in some cases, the persistence of current account deficits. It then examines some peculiar features of the growth experience under monetary union in four Euro area countries which do not conform to the conventional convergence pattern. Models establishing the optimality of a succession of current account deficits in a catching-up process implicitly assume that the intertemporal budget constraint is satisfied, so that the accumulation of foreign liabilities is matched by future surpluses. In section 3 we first introduce explicitly this constraint in a simple two-period, two-good model and show that its fulfilment requires that growth be driven by an adequate increase of the country's production capacity of traded goods and services. By examining the composition of output and demand we show that this has not been the case in the four countries considered and argue that monetary union has helped relax the necessary discipline. The common monetary policy moreover did nothing to prevent an extraordinary growth of credit that fed the imbalances in the four countries. The paper closes addressing some policy issues related to the future sustainability o the monetray union.

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Financial systems are inherently fragile because of the very function which makes them valuable: liquidity transformation. Thus regulatory reforms, as urgent and desirable as they are, will definitely strengthen the financial system and decrease the risk of liquidity crises, but they will never eliminate it. This leaves monetary policy with a very important task. In a framework that recognizes the interactions between monetary policy and liquidity transformation 'optimal' monetary policy would consist of a modified Taylor rule in which the real rate reflects the possibility of liquidity crises and recognizes the possibility that liquidity transformation gets ubsidized. Failure to recognize this point risks leading the economy into a low interest rate trap: low interest rates induce too much risk taking and increase the probability of crises. These crises, in turn, require low interest rates to maintain the ...nancial system alive. Raising rates becomes extremely difficult in a severely weakened financial system, so monetary authorities remain stuck in a low interest rates trap. This seems a reasonable description of the situation we have experienced throughout the past decade.

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In this paper, we provide new evidence on the determinants of sovereign yield spreads and contagion effects in the euro area in order to evaluate the rationale for a common Eurobond jointly guaranteed by euro-area Member States. We find that default risk is the main driver of yield spreads, suggesting small gains from greater liquidity. Fiscal fundamentals matter in the pricing of default risk but only as they interact with other countries' yield spreads; i.e. with the global risk that the market perceives. More important, the impact of this global risk variable is not constant over time, a clear sign of contagion driven by shifts in market sentiment. This evidence points to a discontinuity in the disciplinary role of financial markets. If markets can stay irrational longer than a country can stay solvent, then the role of yield spreads on national bonds as a fiscal discipline device is considerably weakened, and issuing Eurobonds can be economically justified.

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We bring together the theories of duality and dynamic programming. We show that the dual of an additively separable dynamic optimization problem can be recursively decomposed using summaries of past Lagrange multipliers as state variables. Analogous to the Bellman decomposition of the primal problem, we prove equality of values and solution sets for recursive and sequential dual problems. In non-additively separable settings, the equivalence of the recursive and sequential dual is not guaranteed. We relate recursive dual and recursive primal problems. If the Lagrangian associated with a constrained optimization problem admits a saddle then, even in non-additively separable settings, the values of the recursive dual and recursive primal problems are equal. Additionally, the recursive dual method delivers necessary conditions for a primal optimum. If the problem is strictly concave, the recursive dual method delivers necessary and sufficient conditions for a primal optimum. When a saddle exists, states on the optimal dual path are subdifferentials of the primal value function evaluated at states on the optimal primal path and vice versa.

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Banks provide credit and take deposits. Whereas a high price in the credit market increases banks' retained earnings and attracts more deposits, it reduces lending if borrowers are sufficiently poor to be tempted by diversion. Thus optimal bank market structure trades off the benefits of monopoly banking in attracting deposits against losses due to tighter credit. The model shows that market structure is irrelevant if both banks and borrowers lack resources. Monopoly banking induces tighter credit rationing if borrowers are poor and banks are wealthy, and increases lending if borrowers are wealthy and banks lack resources. The results indicate that improved legal protection of creditors is a more efficient policy choice than legal protection of depositors, and that subsidies to firms lead to better outcomes than subsidies to banks. There are also likely to be sizable gains from promoting bank competition in developing countries.

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We build a model where a dark pool is introduced to a transparent limit order book market. We show that orders are diverted to the dark pool, but more orders are also executed so total volume increases especially when the order book is shallow. A smaller spread, greater depth and larger tick size stimulate order migration to the dark pool. Institutional traders always benefit from having access to the dark pool. Market quality and retail traders' welfare deteriorate when the order book is shallow, but improve when it is deep. These effects are stronger for a continuous than for a periodic dark pool. If pre-trade transparency is required, the effects on market quality and retail traders' welfare are magnified if the dark pool executes periodically but do not change significantly if the dark pool is continuous.

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A dominant firm undertakes a given business practice that is regulated by an antitrust enforcer by the choice of a legal standard, fines and accuracy. In traditional industries the incumbent and technology are already established, while in innovative industries the successful innovator becomes dominant. In the former case, marginal deterrence is key to enforcement, and discriminating rules are always dominant when fines are unbounded, or they are replaced with per-se illegality when fines are capped and the practice is likely to be socially harmful. In innovative industries marginal deterrence interacts with average deterrence (the impact of enforcement on innovation eort). Then, per-se legality is preferred when the practice is likely to be welfare beneficial, moving to a discriminating rule when social harm becomes more likely. When fines are capped, per se-legality, discriminating rule and per-se illegality are alternatively chosen when the practice is more and more likely to be socially harmful.

We build an agent-based simulation model that incorporates both historical data on population characteristics and spatial information on the geography of France to experimentally study the role of social interactions in fertility decisions. We assess how different behavioural and interdependence assumptions cause variations in macro dynamics and diffusion patterns. The analyses show that incorporating social interactions into the model contribute to mimic empirically observed behaviour. Our findings suggest individual-level mechanisms through which the observed demographic transition was materialised.