Estimation of Stratified Mark‐Specific Proportional Hazards Models with Missing Marks

Abstract. An objective of randomized placebo‐controlled preventive HIV vaccine efficacy trials is to assess the relationship between the vaccine effect to prevent infection and the genetic distance of the exposing HIV to the HIV strain represented in the vaccine construct. Motivated by this objective, recently a mark‐specific proportional hazards (PH) model with a continuum of competing risks has been studied, where the genetic distance of the transmitting strain is the continuous ‘mark’ defined and observable only in failures. A high percentage of genetic marks of interest may be missing for a variety of reasons, predominantly because rapid evolution of HIV sequences after transmission before a blood sample is drawn from which HIV sequences are measured. This research investigates the stratified mark‐specific PH model with missing marks where the baseline functions may vary with strata. We develop two consistent estimation approaches, the first based on the inverse probability weighted complete‐case (IPW) technique, and the second based on augmenting the IPW estimator by incorporating auxiliary information predictive of the mark. We investigate the asymptotic properties and finite‐sample performance of the two estimators, and show that the augmented IPW estimator, which satisfies a double robustness property, is more efficient.     

WHAT IS HAPPENING TO THE IMPACT OF FINANCIAL DEEPENING ON ECONOMIC GROWTH?

Although the finance‐growth relationship is now firmly entrenched in the empirical literature, we show that it is not as strong in more recent data as it was in the original studies with data for the period from 1960 to 1989. We consider several explanations. First, we find that the incidence of financial crises is related to the dampening of the effect of financial deepening on growth. Excessive financial deepening or too rapid a growth of credit may have led to both inflation and weakened banking systems which in turn gave rise to growth‐inhibiting financial crises. Excessive financial deepening may also be a result of widespread financial liberalizations in the late 1980s and early 1990s in countries that lacked the legal or regulatory infrastructure to exploit financial development successfully. However, we find little indication that liberalizations played an important direct role in reducing the effect of finance. Similarly, there is little evidence that the growth of equity markets in recent years has substituted for debt financing and led to a reduced role of financial deepening on growth. (JEL E44, G10, O40)     

Psycho-Drama as a Medium for Intermediate Treatment

Summary This paper is an account of an Intermediate Treatment Groupset up in February 1975. It uses spontaneous drama as its onlyactivity. It is argued that this provides general personal growthin a supportive atmosphere as well as allowing experimentationwith specific problem situations. The methods used are describedand an attempt is made to discuss the dynamics involved in theseprocesses.     

ENVIRONMENTAL REGULATION: WHOSE SELF-INTERESTS ARE BEING PROTECTED?

Special interest can explain why environmental policy limits economic activity in areas where air quality is above minumum standards. Locational competition among region helped create a policy that raised factor mobility cost from slower to faster growing regions. Analysis of votes shows greater support for this policy was received from northern urban constituencies and the greatest opposition came from the South and the West. Pollution abatement costs per unit of output are higher in areas with higher not lower air quality.     

Work,family and the care of children: issues of equality and responsibility

SUMMARY. The current growth in women's employment, particularly among women with young children, gives new prominence to an issue of major political, economic and social importance, involving men as well as women and children: the relationship between paid work and family responsibilities and how to reconcile these demands without creating inequalities or stress for children or parents, especially mothers. The paper considers the Government's response to this development, arguing that it should be taking a strategic or leadership role, working in active partnership with employers, trades unions, local authorities, voluntary organisations and parents. Examples from Sweden, Spain and New Zealand are given to illustrate this alternative approach     

PRODUCT DIFFERENTIATION UNDER CONGESTION: HOTELLING WAS RIGHT

We introduce negative network externalities—“congestion costs”—into H. Hotelling's (1929) model of spatial competition with linear transportation costs. For any firm locations on opposite sides of the midpoint, a pure strategy price equilibrium exists and is unique if congestion costs are strong enough relative to transportation costs. We analyze product differentiation and find that Hotelling's Principle of Minimum Differentiation comes closer to holding in the presence of congestion costs. The greater are congestion costs, the less differentiated products can be in (locationally symmetric) equilibrium. In fact, minimum differentiation comes arbitrarily close to holding depending on the magnitude of these costs relative to transportation costs. Intuitively, greater congestion effects stabilize competition at closer quarters, eliminating aggressive pricing equilibria. Thus, negative network externalities can play a significant role in product differentiation. (JEL D21, L15, R12)