Non-parametric inference for the effect of a treatment on survival times with application in the health and social sciences

In this paper we perform inference on the effect of a treatment on survival times in studies where the treatment assignment is not randomized and the assignment time is not known in advance. Two such studies are discussed: a heart transplant program and a study of Swedish unemployed eligible for employment subsidy. We estimate survival functions on a treated and a control group which are made comparable through matching on observed covariates. The inference is performed by conditioning on waiting time to treatment, that is, time between the entrance in the study and treatment. This can be done only when sufficient data are available. In other cases, averaging over waiting times is a possibility, although the classical interpretation of the estimated survival functions is lost unless hazards are not functions of waiting time. To show unbiasedness and to obtain an estimator of the variance, we build on the potential outcome framework, which was introduced by J. Neyman in the context of randomized experiments, and adapted to observational studies by D.B. Rubin. Our approach does not make parametric or distributional assumptions. In particular, we do not assume proportionality of the hazards compared. Small sample performance of the estimator and a derived test of no treatment effect are studied in a Monte Carlo study.     

INDEX TO VOLUME 5 (1987)

Real-time estimates of output gaps and inflation gaps differ from the values that are obtained using data available long after the event. Part of the problem is that the data on which the real-time estimates are based is subsequently revised. We show that vector-autoregressive models of data vintages provide forecasts of post-revision values of future observations and of already-released observations capable of improving estimates of output and inflation gaps in real time. Our findings indicate that annual revisions to output and inflation data are in part predictable based on their past vintages. This article has online supplementary materials.     

Multimarket pioneers: Does multimarket contact improve their performance?

First-mover advantages (FMA) and multimarket contact (MMC) have evolved independently in the strategic management literature. This is surprising because FMA erode as a result of competition which, in turn, is affected by MMC. This paper links these literatures through the concept of spheres of influence and analyses the effect of MMC on pioneers' profitability. We use the order of market entry to identify spheres of influence and to determine their distribution among multimarket firms. The distribution of spheres of influence allows us to distinguish between reciprocal MMC and non-reciprocal MMC and to study how each of them determines pioneers' profitability. We test our hypotheses in the mobile telecommunications industry. Our findings show that reciprocal MMC has a positive effect on pioneers’ results, but non-reciprocal MMC negatively affects them.     

Jackknifed kernel quantile estimators

A new quantile estimator is obtained by jackknifing the kernel quantile estimator. The asymptotic relative deficiency of the kernel quantile estimator relative to the jackknifed quantile estimator is investigated.     

Pretending emotions in the early years: The role of language and symbolic play

Although 3-year-old children sometimes simulate emotions to adapt to social norms, we do not know if even younger children can pretend emotions in playful contexts. The present study investigated (1) what emotions infants of 1–2 years old are capable of pretending and (2) the possible role of language and symbolic play in the ability to pretend emotions. The sample included 69 infants aged 18 to 31 months and their parents. Infants were administrated the Test of Pretend Play, and their parents responded to the MacArthur-Bates CDI-II inventory, part of the MacArthur-Bates CDI-I, and a questionnaire about the expression of pretend emotions. Results suggest that very young children simulate emotions. Furthermore, children's simulation of emotions was related to both symbolic play and language. Specifically, the ability to label emotions was linked to the ability to simulate them. The role of language and symbolic play in the development of the capacity to express and understand pretend emotions is discussed.     

Comparative assessment of analytical approaches to quantify the risk for introduction of rare animal diseases: the example of avian influenza in Spain

Trade of animals and animal products imposes an uncertain and variable risk for exotic animal diseases introduction into importing countries. Risk analysis provides importing countries with an objective, transparent, and internationally accepted method for assessing that risk. Over the last decades, European Union countries have conducted probabilistic risk assessments quite frequently to quantify the risk for rare animal diseases introduction into their territories. Most probabilistic animal health risk assessments have been typically classified into one-level and multilevel binomial models. One-level models are more simple than multilevel models because they assume that animals or products originate from one single population. However, it is unknown whether such simplification may result in substantially different results compared to those obtained through the use of multilevel models. Here, data used on a probabilistic multilevel binomial model formulated to assess the risk for highly pathogenic avian influenza introduction into Spain were reanalyzed using a one-level binomial model and their outcomes were compared. An alternative ordinal model is also proposed here, which makes use of simpler assumptions and less information compared to those required by traditional one-level and multilevel approaches. Results suggest that, at least under certain circumstances, results of the one-level and ordinal approaches are similar to those obtained using multilevel models. Consequently, we argue that, when data are insufficient to run traditional probabilistic models, the ordinal approach presented here may be a suitable alternative to rank exporting countries in terms of the risk that they impose for the spread of rare animal diseases into disease-free countries.     

Open Days for NESB Communities: Primary Prevention for Sexual Abuse

The realisation that cultural contexts were impeding access to services for many disadvantaged families and hindering the disclosure of child sexual abuse prompted two agencies to organise collaborative primary prevention strategies. Family groups were convened from the local Cambodian, Vietnamese, Latin American and Arabic‐speaking communities. Focus groups were attended by one or more members of each family. Participants contributed to the formation of a collective understanding that could then be adapted and passed on to other families in their communities. It was observed that once individual families entered this process, isolation diminished and steps towards exploration of the issues could be taken. This paper outlines a process through which family therapists can use primary prevention strategies to reach NESB groups.