04.01. Lobato, I., y Velasco, C., "Optimal Fractional Dickey-Fuller Tests for Unit Roots" 

Resumen: This article studies the fractional Dickey- Fuller (FDF) test for unit roots recently introduced by Dolado, Gonzalo and Mayoral (2002). Apart from the analogy with the Dickey-Fuller test, the main motivation for their method relies on simulations since these authors do not provide any justification for their particular implementation of the FDF test. In order to give additional rationale to the test, we frame the FDF test in a model where a nuisance or auxiliary parameter is not identified under the null hypothesis. Within this framework we investigate optimality aspects of the class of tests indexed by this auxiliary parameter and show that the test proposed by these authors is not optimal. In addition, we propose feasible FDF tests with good asymptotic and finite sample properties.

04-02. Maurer, N., y  Gomberg, A., "When the State is Untrustworthy: Public Finance and Private Banking in Porfirian Mexico" 

Resumen: All sovereign governments face a commitment problem: how can they promise to honor their own agreements? The standard solutions involve reputation or political institutions capable of tying the hands of the government. Mexico's government in the 1880s used neither solution. It compensated its creditors by enabling them to extract rents from the rest of the economy. These rents came through special privileges over banking services and the right to administer federal taxes. Returns were extremely high: as long as creditors believed that the government would refrain from confiscating all their assets (let alone repaying their debts) less than twice a decade, they would break even.

04-03. Sadka, J., y J. L. Negrín., "Full vs. Light-Handed Regulation of a Network Industry" 

Resumen: The access pricing problem emerges when a vertically integrated firm (the incumbent) provides an essential service in the upstream market, to an entrant. Both firms produce a final service and compete in the downstream market. The standard treatment of this problem has been to add the access price to the list of instruments available to a regulator who maximizes a social welfare function. Motivated by the international trend to reduce the number of prices set by regulation, we use a light handed regulation approach in which the only tool available to the regulator is the access price, and where retail prices are set by quantity competition in the downstream market. In this setup, we find that a regulator seeking to maximize total market surplus will set an access price that subsidizes the entrant, so that entrants that are less efficient than the incumbent firm can survive in the market. We then compare the outcomes of the full regulation model with those of the light-handed regulation model, in terms of final prices, firm profits, and consumer surplus. When the regulator faces incomplete information about entrant firms' costs and cannot offer a menu of contracts to potential entrants, we find examples in which light handed regulation can dominate full regulation.

04-04. Martinelli, C., y R. Sicotte., "Voting in Cartels: Theory and Evidence from the Shipping Industry" 

Resumen: We examine the choice of voting rules by legal cartels with enforcement capabilities in the presence of uncertainty about demand and costs. We show that cartels face a trade-off between the commitment advantages of more stringent majority requirements and the loss of flexibility resulting from them. Expected heterogeneity in costs or demand conditions leads away from simple majority toward more stringent rules, while larger membership to the cartel leads away from unanimity toward less restrictive rules. Evidence from the shipping conferences of the late 1950s largely supports our model. With few firms, the rule favored by heterogeneous conferences is unanimity. In larger cartels, the favored rule is either 2/3 or 3/4-majority rule.

04-05. Lobato, I., S. Pratap., y A. Somuano., "Debt Composition and Balance Sheet Effects of Exchange Rate Volatility in Mexico: A Firm Level Analysis" 

Resumen: We use Mexican firm-level data to study the role of currency mismatches in exacerbating the negative effects of a devaluation in the corporate sector and to investigate what drives Mexican firms to borrow in foreign currency. Our results show that large firms and exporters tend to borrow more heavily in foreign currency. The presence of foreign currency denominated debt poses a significant risk to balance sheets at the time of devaluation. Our findings suggest that in Mexico, the balance sheet effects of a devaluation far outweigh the competitiveness effects.

04-06. Pratap, S., y C. Urrutia., "Firm Dynamics, Investment, and Debt Portfolio: Balance Sheet Effects of the Mexican Crisis of 1994" 

Resumen: We build a partial equilibrium model of firm dynamics under exchange rate uncertainty. Firms face idiosyncratic productivity shocks and observe the current level of the real exchange rate each period. Given their current level of capital stock, firms make their export decisions and choose how much to invest. Investment is financed through one period loans from foreign lenders. The interest rate charged by each lender is set to satisfy an expected zero-profit condition. The model delivers a distribution of firms over productivity, capital stocks and debt portfolios, as well as an exit rule. We calibrate the model using data from a panel of Mexican firms, from 1989 to 2000, and analyze the effect of the 1994 crisis on these variables. As a result of the real exchange rate depreciation, the model predicts: (i) an increase in the debt burden, (ii) an increase in exports, and (iii) a large decline in investment. These real effects are consistent with the evidence for the Mexican crisis.

04-07. Elbittar, A., A. Gomberg, y L. Sour., "Group Decision-Making in Ultimatum Bargaining: An Experimental Study " 

Resumen: Many rent-sharing decisions in a society are result from a bargaining process between groups of individuals (such as between the executive and the legislative branches of government, between legislative factions, between corporate management and shareholders, etc.). The purpose of this work is to conduct a laboratory study of the effect of different voting procedures on group decision-making in the context of ultimatum bargaining. An earlier study (Bornstein and Yaniv, [2]) has suggested that when the bargaining game is played by unstructured groups of agents, rather than by individuals, the division of the payoff is substantially affected in favor of the ultimatum-proposers. Our theoretical arguments suggest that one explanation for this could be implicit voting rules within groups. We propose to explicitly structure the group decision-making as voting and study the impact of different voting rules on the bargaining outcome.

04-08. Martinelli, C., y R. Escorza., "When Are Stabilizations Delayed? Alesina-Drazen Revisited" 

Resumen: In an influential article, Alesina and Drazen (1991) model delay of stabilization as the result of a struggle between political groups supporting reform plans with different distributional implications. In this paper we show that ex ante asymmetries in the costs of delay for the groups will reduce the probability of conflict and will lead to a shorter expected delay. Accurate common information about the cost of delay may lead to no delay at all. In an asymmetric conflict, a wider divergence in the distributional implications of reform will reduce the probability of conflict but will lead to a longer expected delay.

04-09. Rojas, J. A., y C. Urrutia., "Social Security Reform with Uninsurable Income Risk and Endogenous Borrowing Constraints" 

Resumen: We study the aggregate effects of a social security reform in a large overlapping generations model where markets are incomplete and households face uninsurable idiosyncratic income shocks. We depart from the previous literature by assuming that, because of lack of commitment in the credit market, the borrowing constraint in the unique asset is endogenously determined by the agents' incentives to default on previous debts. We find that a model with exogenous borrowing constraints overestimates the positive effect of reforming social security on the capital stock and the saving rate, compared to our model with endogenous borrowing limit. The reason is that, in the latter, the size of precautionary savings is smaller because after the reform the incentives to default on previous debts are lower and consequently households face more relaxed borrowing limits. Adding retirement accounts to the basic model does not change these conclusions, although the quantitative importance of endogenizing borrowing constraints is reduced.