A play-the-winner-type urn design with reduced variability

We propose a new adaptive allocation rule, the drop-the-loser, that randomizes subjects in the course of a trial comparing treatments with dichotomous outcomes. The rule tends to assign more patients to better treatments with the same limiting proportion as the randomized play-the-winner rule. The new design has significantly less variable allocation proportion than the randomized play-the-winner rule. Decrease in variability translates into a gain in statistical power. For some values of success probabilities the drop-the-loser rule has a double advantage over conventional equal allocation in that it has better power and assigns more subjects to the better treatment. Acknowledgments. I thank Stephen Durham, the associate editor, and the referees for their helpful suggestions.     

Estimating panel data models in the presence of endogeneity and selection

We consider estimation of panel data models with sample selection when the equation of interest contains endogenous explanatory variables as well as unobserved heterogeneity. Assuming that appropriate instruments are available, we propose several tests for selection bias and two estimation procedures that correct for selection in the presence of endogenous regressors. The tests are based on the fixed effects two-stage least squares estimator, thereby permitting arbitrary correlation between unobserved heterogeneity and explanatory variables. The first correction procedure is parametric and is valid under the assumption that the errors in the selection equation are normally distributed. The second procedure estimates the model parameters semiparametrically using series estimators. In the proposed testing and correction procedures, the error terms may be heterogeneously distributed and serially dependent in both selection and primary equations. Because these methods allow for a rather flexible structure of the error variance and do not impose any nonstandard assumptions on the conditional distributions of explanatory variables, they provide a useful alternative to the existing approaches presented in the literature.     

Endogenous Transport Coefficients: Implications for Improving Water Quality from Multi-Contaminants in an Agricultural Watershed

The effectiveness of imperfect pollution control instruments is examined for a diffuse source, multi-contaminant problem in which the transport coefficients for sediment-bound residuals are endogenous. Similar evaluations fix the percentage of sediment deposited and optimize either for a single firm managing the whole watershed or on a firm by firm basis. This study shows that ignoring the dependence of the transport coefficients on intervening land uses creates a positive externality. The filtering potential of activities conducted by firms close to the receptor permits firms further away to undertake more profitable but erosive practices. Optimizing management choices, and consequently endogenizing the transport coefficients, for all firms simultaneously removes the externality. An empirical application combines hydrological simulation models with an economic optimization model for nutrient pollution of surface and ground water within an agricultural watershed. Although firms are homogeneous in abatement costs, differences in spatial location leave uniform instruments unable to achieve the water quality goal efficiently. An ambient tax/subsidy scheme can achieve the water quality goal efficiently but the informational requirements will be excessive in most situations where the transport mechanisms for residuals are dependent upon the practices of independent decision making units.     

Entrepreneurs' responses to semi-formal illegitimate institutional arrangements

While prior research has discussed how entrepreneurs deal with formal institutional voids and informal institutional environments, little is known about how entrepreneurs respond to institutional arrangements involving illegitimate actors. We define such arrangements as semi-formal illegitimate institutions. Using an exploratory study, we examine one such arrangement in Guatemala City, where organized crime dominates the institutional landscape in which entrepreneurs operate. We examine the strategic responses of these entrepreneurs, and find that they vary in the extent to which they resist semi-formal illegitimate institutions; some entrepreneurs engage in defiance, others avoid the illegitimate pressures, while others simply acquiesce. Upon further investigation, we find that the differences in entrepreneurs' network strength and network proximity, combined with their individual perception of threat and resource mobility, help to predict the different strategic responses.     

Profit efficiency in the European Union banking industry: a directional technology distance function approach

We employ the directional technology distance function approach and present estimates of profit efficiency in the 25 European Union (EU) member states over the period 1998–2008. This method decomposes profit efficiency into its technical and allocative components. We investigate potential efficiency differences across the old EU region and the new EU member states, across countries and across banks of different size. Our results indicate a significant level of profit inefficiency for the EU region, which is predominantly attributed to allocative inefficiency. Our findings also suggest that banks operating in the old EU region are, on average, more profit efficient than credit institutions in the new EU member states. Overall, we observe considerable variation of efficiency scores across countries and different patterns in efficiency change over time, as well as a negative relationship between bank size and efficiency.