A non-parametric independence test using permutation entropy

In the present paper we construct a new, simple, consistent and powerful test for independence by using symbolic dynamics and permutation entropy as a measure of serial dependence. We also give a standard asymptotic distribution of an affine transformation of the permutation entropy under the null hypothesis of independence. The test statistic and its standard limit distribution are invariant to any monotonic transformation. The test applies to time series with discrete or continuous distributions. Eventhough the test is based on entropy measures, it avoids smoothed non-parametric estimation. An application to several daily financial time series illustrates our approach.     

Real Options Valuation: A Case Study of an E‐commerce Company

This paper presents a real options valuation model with original solutions to some issues that arise frequently when trying to apply these models to real‐life situations. The authors build on existing models by introducing an innovative and intuitive risk neutral adjustment that allows us to work with all the simulated paths. The problem of incorporating real options into each path is solved with a “nearest neighbors” technique, and uncertainty is simulated using a beta distribution that adapts better to company‐specific information. The model is then applied to a real life e‐commerce company to produce the following insights: the expanded present value is higher than the traditional present value; the presence of several real options make them interact so that their values are nonadditive; and part of the expanded present value is explained by the presence of “Jensen's inequality” that stems from the “convexity” between the value of each year's cash flow and the uncertain variables.     

Neural network volatility forecasts

We analyse whether the use of neural networks can improve ‘traditional’ volatility forecasts from time-series models, as well as implied volatilities obtained from options on futures on the Spanish stock market index, the IBEX-35. One of our main contributions is to explore the predictive ability of neural networks that incorporate both implied volatility information and historical time-series information. Our results show that the general regression neural network forecasts improve the information content of implied volatilities and enhance the predictive ability of the models. Our analysis is also consistent with the results from prior research studies showing that implied volatility is an unbiased forecast of future volatility and that time-series models have lower explanatory power than implied volatility. Copyright © 2008 John Wiley & Sons, Ltd.     

Differentiable strategy-proof mechanisms for private and public goods in domains that are not necessarily large or quasi-linear

In this paper, we develop a differentiable approach to deal with incentives in a, possibly small, subset of a general domain of preferences in economies with one public and one private good. We show that, for two agents, there is no mechanism which is efficient, strategy-proof and where consumption of both goods is positive for all agents. For the case of two or more agents the same result occurs when nondictatorship is replaced by Individual Rationality. We are very grateful to Atila Abdulkadiroglu, Carmen Beviá, Xavier Calsamiglia, Marco Celentani, Bernardo Moreno, Antonio Romero-Medina, William Thomson, Walter Trockel, an associate editor, three anonymous referees and participants at seminars at Universities of Alicante, Autónoma de Barcelona and Rochester and the Spanish Economic Association meeting in Sevilla for very helpful comments and suggestions.     

Rubinstein bargaining with two-sided outside options

Summary. In this note we show that if in the standard Rubinstein model both players are allowed to leave the negotiation after a rejection, in which case they obtain a payoff of zero, then there exist a continuum of subgame-perfect equilibrium outcomes, including some which involve significant delay. We also fully characterize the case in which, upon quitting, the players can take an outside option of positive value. Received: February 27, 1996; revised version: March 28, 1997     

The New Member States and the Process towards EMU

The authors apply two complementary empirical criteria to eight new member states (NMSs) of the European Union to assess how ready they are to adopt the euro. As a first step, they recover demand and supply shocks and calculate the social losses implied by the two relevant exchange rate regimes: flexible rates and currency board. As a second step, the authors calculate the real exchange rates variability that these countries are currently experiencing and compare it to that of three Mediterranean countries during a similar period before they joined the EMU. The combination of the results of both tests shows that Estonia and Slovenia are the only countries that seem ready to adopt the euro within the shortest period of time foreseen by the Maastricht criteria; that is, after the two mandatory years in the ERM2. The rest of the countries will probably still need some exchange rate flexibility to absorb external shocks in the coming years.     

AHP-Group Decision Making: A Bayesian Approach Based on Mixtures for Group Pattern Identification

This paper proposes a Bayesian estimation procedure to determine the priorities of the Analytic Hierarchy Process (AHP) in group decision making when there are a large number of actors and a prior consensus among them is not required. Using a hierarchical Bayesian approach based on mixtures to describe the prior distribution of the priorities in the multiplicative model traditionally used in the stochastic AHP, this methodology allows us to identify homogeneous groups of actors with different patterns of behaviour for the rankings of priorities. The proposed procedure consists of a two-step estimation algorithm: the first step carries out a global exploration of the model space by using birth and death processes, the second concerns a local exploration by means of Gibbs sampling. The methodology has been illustrated by the analysis of a case study adapted from a real experiment on e-democracy developed for the City Council of Zaragoza (Spain). Partially funded under the research project Electronic Government. Internet-based Complex Decision Making: e-democracy and e-cognocracy (Ref. PM2004-052) approved by the Regional Government of Aragon (Spain) as part of the multi-disciplinary projects programme.     

Information acquisition and financial contagion

This paper incorporates costly voluntary acquisition of information à la Nikitin and Smith (2007) [Nikitin, M., Smith, R.T., 2007. Information acquisition, coordination, and fundamentals in a financial crisis. Journal of Banking and Finance, in press, doi:10.1016/j.jbankfin.2007.04.031], in a framework similar to Allen and Gale (2000) [Allen, F., Gale, D., 2000. Financial contagion. Journal of Political Economy 108, 1–33], without relying on any unexpected shock to model contagion. In this framework, contagion and financial crises are the result of information gathering by depositors, weak fundamentals and an incomplete market structure of banks. It also shows how financial systems entering a recession can affect others with apparently stronger economic conditions (contagion). Finally, this is the first paper to investigate the effectiveness of the Contingent Credit Line procedures, introduced by the IMF at the end of the nineties, as a mechanism to prevent the propagation of crises.