Secrecy, two-sided bias and the value of evidence

We provide necessary and sufficient conditions on players' preferences for a verifiable message game to possess a separating equilibrium and/or a pooling equilibrium, as well as sufficient conditions for every equilibrium of such a game to be pooling. We also characterize all nonseparating equilibria, and use this property to show that less information might be conveyed in any equilibrium of a verifiable message game than in some equilibrium of the cheap talk game with the same parameters.     

Climate change impacts on irrigation water requirements: Effects of mitigation, 1990–2080

Potential changes in global and regional agricultural water demand for irrigation were investigated within a new socio-economic scenario, A2r, developed at the International Institute for Applied Systems Analysis (IIASA) with and without climate change, with and without mitigation of greenhouse gas emissions. Water deficits of crops were developed with the Food and Agriculture Organization (FAO)–IIASA Agro-ecological Zone model, based on daily water balances at 0.5° latitude × 0.5° longitude and then aggregated to regions and the globe. Future regional and global irrigation water requirements were computed as a function of both projected irrigated land and climate change and simulations were performed from 1990 to 2080. Future trends for extents of irrigated land, irrigation water use, and withdrawals were computed, with specific attention given to the implications of climate change mitigation. Renewable water-resource availability was estimated under current and future climate conditions. Results suggest that mitigation of climate change may have significant positive effects compared with unmitigated climate change. Specifically, mitigation reduced the impacts of climate change on agricultural water requirements by about 40%, or 125–160 billion m³ (Gm³) compared with unmitigated climate. Simple estimates of future changes in irrigation efficiency and water costs suggest that by 2080 mitigation may translate into annual cost reductions of about 10 billion US$.     

Wage Flexibility and Unemployment: The Keynesian Perspective Revisited

Keynes' main concern in the General Theory is about the capacity of an economy to return to full employment equilibrium when subject to a (negative) demand shock. He maintains that money wages cuts may not help reabsorb unemployment, as they do not necessarily imply a fall in real wages. On the contrary, wage rigidity may be necessary for avoiding that a cumulative process propels the economy far away the full employment equilibrium. Co‐ordination failures in the investment‐saving market are behind this conclusion. However, the analysis is carried out within a static equilibrium framework. This paper is an attempt to focus on the problems of intertemporal co‐ordination arising within the context of a sequential economy. Our analysis of the out‐of‐equilibrium process of adjustment stirred by a shock allows to generalize the original Keynesian intuition. Unemployment emerges as the result of a lack of co‐ordination due to irreversibly constrained choices, and not only nominal but also real wage flexibility does not necessarily help to restore equilibrium. As a matter of fact, it may even be harmful, by triggering processes that make the economy diverge from equilibrium. Our analysis has important analytical implications as regards the role of market imperfections and the interpretation of the effects of monetary policy.     

Surface movement ground control by means of a GPS–GIS system

Despite the traffic increases at the World's airports, little works have been done on methodologies to improve vehicles and airplanes ground control. This may be leading to reduced safety. Here an integrated system is developed to help guarantee suitable separations of land vehicles and airplanes moving on the airport ground area It can also addressed issues of the optimal use of taxi and runways. The system is composed of global positioning systems hardware, checks on the position of land vehicles and airplanes on the ground in real time, and special-purpose geographical information systems software for the tracking of land vehicles and airplanes within different planning operations.     

Extracting information or resource? The Hotelling rule revisited under asymmetric information

A concessionaire has private information on the initial stock of resource. A “virtual Hotelling rule” describes how the resource price evolves over time and how extraction costs are compounded with information costs along the optimal extraction path. Fields which are heterogeneous in terms of their initial stocks follow different extraction paths. Resource might be left unexploited in the long run as a way to foster incentives. The optimal contract may sometimes be implemented through royalties and license fees. With a market of concessionaires, asymmetric information leads to a “virtual Herfindahl principle” and to another form of heterogeneity across active concessionaires.     

On the Generic Finiteness of Equilibrium Outcomes in Plurality Games

In this paper we prove that for generic (noncooperative) voting games under plurality rule the set of equilibria that induce a mixed distribution over the outcomes (i.e., with two or more candidates elected with positive probability) is finite and, furthermore, each of these equilibria is regular. From that we deduce the finiteness of the set of equilibrium distributions over outcomes. Furthermore we offer an example (S. Govindan and A. McLennan, 1997, “On the Generic Finiteness of Equilibrium Outcome Distributions in Game Forms,” mimeo) that shows the impossibility of extending such results to a general framework, even just to voting games. Journal of Economic Literature Classification Numbers: C72, D72.     

On loss functions and ranking forecasting performances of multivariate volatility models

The ranking of multivariate volatility models is inherently problematic because when the unobservable volatility is substituted by a proxy, the ordering implied by a loss function may be biased with respect to the intended one. We point out that the size of the distortion is strictly tied to the level of the accuracy of the volatility proxy. We propose a generalized necessary and sufficient functional form for a class of non-metric distance measures of the Bregman type which ensure consistency of the ordering when the target is observed with noise. An application to three foreign exchange rates is provided.     

A Remark on Voters' Rationality in a Model of Representative Democracy

Voting games are characterized by the emergence of dominated strategies, that would be iteratively deleted by rational players. In this note we show, via an example, how applying iterated dominance restricts the set of equilibrium outcomes in Besley and Coate's (1997) citizen-candidate model of representative democracy.     

HEDGING WITH ENERGY

In the setting of diffusion models for price evolution, we suggest an easily implementable approximate evaluation formula for measuring the errors in option pricing and hedging due to volatility misspecification. The main tool we use in this paper is a (suitably modified) classical inequality for the L ² norm of the solution, and the derivatives of the solution, of a partial differential equation (the so-called "energy" inequality). This result allows us to give bounds on the errors implied by the use of approximate models for option valuation and hedging and can be used to justify formally some "folk" belief about the robustness of the Black and Scholes model. Surprisingly enough, the result can also be applied to improve pricing and hedging with an approximate model. When statistical or a priori information is available on the "true" volatility, the error measure given by the energy inequality can be minimized w.r.t. the parameters of the approximating model. The method suggested in this paper can help in conjugating statistical estimation of the volatility function derived from flexible but computationally cumbersome statistical models, with the use of analytically tractable approximate models calibrated using error estimates.