Spatial Regression Models Using Inter-Region Distances in a Non-Random Context

This article considers spatial data z( s ₁), z( s ₂),…, z( s _n ) collected at n locations, with the objective of predicting z( s ₀) at another location. The usual method of analysis for this problem is kriging, but here we introduce a new signal-plus-noise model whose essential feature is the identification of hot spots. The signal decays in relation to distance from hot spots. We show that hot spots can be located with high accuracy and that the decay parameter can be estimated accurately. This new model compares well to kriging in simulations.     

A characterization of majority voting rules with quorums

We give a characterization of majority voting rules with quorums in the framework of May (Econometrica 20:680–684, 1952)’s seminal article. According to these voting rules, an alternative is socially chosen if and only if it obtains the relative majority of votes and the total number of voters not abstaining reaches the quorum.     

Missing values: sparse inverse covariance estimation and?an?extension to sparse regression

We propose an ℓ ₁-regularized likelihood method for estimating the inverse covariance matrix in the high-dimensional multivariate normal model in presence of missing data. Our method is based on the assumption that the data are missing at random (MAR) which entails also the completely missing at random case. The implementation of the method is non-trivial as the observed negative log-likelihood generally is a complicated and non-convex function. We propose an efficient EM algorithm for optimization with provable numerical convergence properties. Furthermore, we extend the methodology to handle missing values in a sparse regression context. We demonstrate both methods on simulated and real data.     

Manaagement practices and employee attitudes: a longitudinal study spanning fifty years

This paper reports findings from a third consecutive study to re‐visit a steelworks that provided a classic elaboration of the industrial enterprise as a social system. The social system of the works in the 1950s (Scott et al., 1956) was used to explain the positive orientation of steelworkers to change. A later study of the plant in 1991 uncovered a remarkably similar positive orientation to change in the plant indicating a number of continuities (Blyton et al., 1996). Despite massive changes affecting the plant between the 1950s and the early 1990s, the social system of the works‐occupational structures and identities and management‐union relations‐were seen as having a continuing bearing on steelworkers’ attitudes to work in general, and their positive orientation to work change in particular. A third study of employee attitudes in the same plant in 1999 revealed important changes had occurred during the 1990s.     

Change in disability-free life expectancy for Americans 70 years old and older*

In this article, we examine changes in life expectancy free of disability using longitudinal data collected from 1984 through 2000 from two cohorts who composed the Longitudinal Studies of Aging I and II. Life expectancies with and without ADL and/or IADL disability are calculated using a Markov-based multistate life table approach. At age 70, disability-free life expectancy increased over a 10-year period by 0.6 of a year in the later cohort, which was the same as the increase in total life expectancy, both increases marginally statistically significant. The average length of expected life with IADL and ADL disability did not change. Changes in disability-free life expectancy resulted from decreases in disability incidence and increases in the incidence of recovery from disability across the two survey cohorts. Age-specific mortality among the ADL disabled declined significantly in the later cohort after age 80. Mortality for the IADL disabled and the nondisabled did not change significantly. Those with ADL disability at age 70 experienced substantial increases in both total life expectancy and disability-free life expectancy. These results indicate the importance of efforts both to prevent and delay disability and to promote recovery from disability for increasing life expectancy without disability. Results also indicate that while reductions in incidence and increases in recovery work to decrease population prevalence of disability, declining mortality among the disabled has been a force toward increasing disability prevalence.     

Lifetime Uncertainty and Time Preference

Despite Fisher's (1930) psychological intuitions of and the formal treatment given by Yaari (1965, Review of Economic Studies 32, 137), the intertemporal model of choice is mainly a model with certain lifetime. The purpose of this paper is to reconsider this assumption, starting from a very simple two-period model of choice with lifetime uncertainty. We examine the comparative statics of the model at the first two orders and replace the concept of `pure time preference' by taking into account the subjective treatment of the probability of survival. This revised version was published online in June 2006 with corrections to the Cover Date.     

COLLABORATE OR CONSOLIDATE: ASSESSING THE COMPETITIVE EFFECTS OF PRODUCTION JOINT VENTURES

We analyze collaborations in which two firms facing external competition reorganize to form an input joint venture as an alternative to horizontal merger. Under standard regularity conditions, the collaboration can lead to higher profits than a horizontal merger, though the effect on prices, quantities, and welfare depends on the form of downstream competition. In light of our results regarding profits, we provide reasons why firms might still wish to merge: imperfect information, cost synergies, and organizational asymmetries. We further consider how our comparisons change with the managerial structure of the joint venture (i.e., by delegation of input pricing). (JEL L13, L23, L42)