Marriage, divorce, and legal change: new evidence from England and Wales

In this article, we explain the evolution of divorce rates in England and Wales over the post-war period. Following the approach of the predominantly North American literature in this area, we focus on the liberalization of divorce law and socioeconomic factors as determinants of the divorce rate. In line with the development of the literature, we find that the introduction of liberalized, no-fault divorce law had a significant effect on the divorce rate in England and Wales. The finding that the law affects the divorce rate is consistent with the view that marriage is characterized by indivisibilities that inhibit Coasian bargaining.     

A theory of quality-related differences in retail margins: why there is a 'premium' on premium gasoline

This paper develops a theory of vertical and horizontal product differentiation to explain observed price-cost margin differentials for goods that differ in quality. The difference in price-cost margins between the high- and low-quality goods is shown to depend positively on consumers' average valuation for incremental increases in quality and positively on the distance to each competitor's closest rival. These predictions are largely supported using an extensive station-level data set of premium and regular unleaded gasoline prices from the Los Angeles Basin area from 1992–1995.     

A score test for overdispersion in Poisson regression based on the generalized Poisson-2 model

Overdispersion is a common phenomenon in Poisson modeling. The generalized Poisson (GP) regression model accommodates both overdispersion and underdispersion in count data modeling, and is an increasingly popular platform for modeling overdispersed count data. The Poisson model is one of the special cases in the collection of models which may be specified by GP regression. Thus, we may derive a test of overdispersion which compares the equi-dispersion Poisson model within the context of the more general GP regression model. The score test has an advantage over the likelihood ratio test (LRT) and over the Wald test in that the score test only requires that the parameter of interest be estimated under the null hypothesis (the Poisson model). Herein, we propose a score test for overdispersion based on the GP model (specifically the GP-2 model) and compare the power of the test with the LRT and Wald tests. A simulation study indicates the proposed score test based on asymptotic standard normal distribution is more appropriate in practical applications.     

Conditional Score Tests for Heteroscedasticity in the Two-Way Error Components Model

This paper extends the one-way heteroskedasticity score test of Holly and Gardiol (2000, In: Krishnakumar, J, Ronchetti, E (Eds.), Panel Data Econometrics: Future Directions, North-Holland, Amsterdam, pp. 199–211) to two conditional Lagrange Multiplier (LM) tests of heteroskedasticity under contiguous alternatives within the two-way error components model framework. In each case, the derivation of Rao's efficient score statistics for testing heteroskedasticity is first obtained. Then, based on a specific set of assumptions, the asymptotic distribution of the score under contiguous alternatives is established. Finally, the expression for the score test statistic in the presence of heteroskedasticity and related asymptotic local powers of these score test statistics are derived and discussed.