What is the weak instruments (WI) problem and what causes it? Universal agreement does not exist on these questions. We define weak instruments by two features: (1) 2SLS is badly biased toward the OLS estimate and alternative “unbiased” estimators such as LIML may not solve the problem and (2) the standard (first order) asymptotic distribution does not give an accurate framework for inference. ...

The use of global suppliers has increased considerably over the last three decades. Operations management theory establishes that global sourcing requires more units of inventory, but since these units are often procured at a lower cost from global suppliers the capital invested in inventory and the consequent financial burden may increase or decrease with global sourcing. This study provides r...

The German Economy is not only affected by the Unification of Germany but by a significant influx of immigrants from abroad and huge migration from East to West Germany around the date of unification. Data from the German Socio-Economic Panel Study (GSOEP) allows to disentangle those effects by decomposition of the Theil I (0)-Index of inequality. In addition, the paper offers insights in the t...

Despite its importance, choosing the structural form of the kernel in nonparametric regression remains a black art. We define a space of kernel structures which are built compositionally by adding and multiplying a small number of base kernels. We present a method for searching over this space of structures which mirrors the scientific discovery process. The learned structures can often decompo...

We study estimation and inference in settings where the interest is in the effect of a potentially endogenous regressor on some outcome. To address the endogeneity we exploit the presence of additional variables. Like conventional instrumental variables, these variables are correlated with the endogenous regressor. However, unlike conventional instrumental variables, they also have direct effec...

Most cases settle, in employment discrimination litigation as elsewhere. Unfortunately, empirical knowledge of settlements remains limited. Data scarcity fuels untested perceptions and, all too frequently, misperceptions about how employment disputes are resolved. This Essay exploits a unique data set of successful settlements in the U.S. District Court for the Northern District of Illinois fro...

We shall show that any two Riemann surfaces satisfying a certain condition, for instance, any two closed surfaces of the same genus g > l , can be uniformized by one group of fractional linear transformations (Theorem 1). This leads, in conjunction with previous results [2; 3] , to the simultaneous uniformization of all algebraic curves of a given genus (Theorems 2-4). Theorem 5 contains an app...

Let R and S be positive integers with R < S. We shall call the simultaneous Diophantine equations x −Ry = 1, z − Sy = 1 simultaneous Pell equations in R and S. Each such pair has the trivial solution (1, 0, 1) but some pairs have nontrivial solutions too. For example, if R = 11 and S = 56, then (199, 60, 449) is a solution. Using theorems due to Baker, Davenport, and Waldschmidt, it is possible...

The three numbers 1, 5, and 442 have the property that the product of any two numbers decreased by 1 is a perfect square. In this paper it is proved that there is no other positive integer which shares this property with 1, 5, and 442. Mathematics Subject Classification: Primary 11D09, 11D25, Secondary 11B37, 11J68, 11J86, 11Y50.

Pakistan constitutes a valuable case study for investigating the dynamics of persistently high rates of budget and current account deficits. In this paper an attempt has been made to empirically test the twin deficits hypothesis in Pakistan using quarterly time-series data for the period 1975 to 2005. The co-integration results indicate the existence of a longrun relationship between the defici...