The value of improved road safety

We report the results of a contingent valuation study for finding a conservative estimate of the value-of-statistical-life in an urban road safety context in Sweden. We estimate the value of both a private-good device and a public-good safety program. The reduction of risk is communicated with a “community analogy” representation of the “Vision Zero” target of the national traffic-safety policy. According to this target, the road-traffic system should be designed so as to prevent accidents when they happen to lead to fatalities or severe injuries. We use the “certainty approach” for ex-post correction of results to remove or mitigate hypothetical bias of responses. As expected we find insensitivity of responses in the full sample to the size of the risk reduction being valued. By our approach we can compute a conservative estimate, based on answers from fully confident respondents, of the value of the largest possible safety enhancement (i.e. fulfilment of the “Vision Zero”). This lower bound estimate indicates a higher average willingness-to-pay for public safety-improving measures than currently assumed in benefit-cost assessments. We also find that the willingness to pay is considerably lower within a public-good than a private-good framework and a weak indication of sensitivity to scale among the most confident respondents. JEL Codes H43 · I18 · Q51     

Treatment‐as‐usual in effectiveness studies: What is it and does it matter?

Andrée Löfholm C, Brännström L, Olsson M, Hansson K. Treatment‐as‐usual in effectiveness studies: What is it and does it matter? A hallmark of an evidence‐based practice (EBP) is the systematic appraisal of research related to the effectiveness of interventions. This study addressed the issue of interpreting results from effectiveness studies that use treatment‐as‐usual (TAU) as a comparator. Using randomised controlled studies that evaluate the effectiveness of multisystemic therapy as an illustrative example, we show that TAU includes a wide variety of treatment alternatives. Estimated treatment effects on recidivism suggest that TAU seems to contain a greater variation in underlying risk than experimental conditions, supporting the hypothesis that the content of TAU could affect outcomes. Implications for the realisation of an EBP are discussed.     

Reducing Requirement Incorrectness and Coping with Its Negative Impact in Information System Development Projects

The negative impact of incorrect requirements on information system development (ISD) project performance has long been acknowledged. This study addresses the problem of incorrect requirements by proposing a model that combines the error reduction and coping concepts proposed by Field, Ritzman, Safizadeh, and Downing (2006) with the view that ISD is a knowledge‐intensive process. The model hypothesizes that when developers and users possess an understanding of each other's primary domain of knowledge, the prevention of incorrect requirements and the mitigation of the negative consequences of incorrect requirements tend to improve project performance. Data collected from 250 ISD professionals on the basis of their experiences of recently completed ISD projects confirmed all of our hypotheses. The results demonstrate that the eliciting of incorrect requirements can be reduced when users and developers possess cross‐domain understanding and when requirement analysis methodologies and techniques are available. Furthermore, the negative impact of incorrect requirements on project performance can be mitigated when developers have sufficient ISD knowledge and behavioral knowledge.     

Quality control procedures at statistics sweden

This paper treats quality control in a wide sense which is imperative for a statistical agencyto do. First, we discuss the meaning of total survey error and different quality characteris-

tics. Secondly, some common quality problems in statistical agencies are presented as a prelude to the bulk of this paper, namely the case of Sweden. Quality control efforts at Statistics Sweden are reviewed regarding the handling of specific error sources, error estimation, and error control. Different tools such as preventive control, production control, and evaluation are dealt with. As for QC-procedures proper we provide some applications from clerical coding.     

Size and Power of Recent Tests for Homogeneity in Exponential Mixtures

The article investigates diagnostic procedures for finite mixture models. The problem is to decide whether given data stem from an exponential distribution or a finite mixture of such distributions. Recently, three new test approaches have been proposed, the modified likelihood ratio test (MLRT) by Chen et al. (2001 Chen , H. , Chen , J. , Kalbfleisch , J. D. ( 2001 ). A modified likelihood ratio test for homogeneity in finite mixture models . Journal of the Royal Statistical Society, B 63 : 19 – 29 .[Crossref] , [Google Scholar]), the ADDS test by Mosler and Seidel (2001 Mosler , K. , Seidel , W. ( 2001 ). Testing for homogeneity in an exponential mixture model . Australian and New Zealand Journal of Statistics 43 : 231 – 247 . [Google Scholar]), and the D-test by Charnigo and Sun (2004 Charnigo , R. , Sun , J. ( 2004 ). Testing homogeneity in a mixture distribution via the l ² distance between competing models . Journal of the American Statistical Society 99 : 488 – 498 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). The size and power of these tests are determined by Monte Carlo simulation and their relative merits are evaluated. We conclude that the ADDS test shows always not much less and under some alternatives, in particular lower contaminations, considerably more power than its competitors. Also, new tables for the ADDS test are provided.     

Long‐Term Risk: An Operator Approach

We create an analytical structure that reveals the long‐run risk‐return relationship for nonlinear continuous‐time Markov environments. We do so by studying an eigenvalue problem associated with a positive eigenfunction for a conveniently chosen family of valuation operators. The members of this family are indexed by the elapsed time between payoff and valuation dates, and they are necessarily related via a mathematical structure called a semigroup. We represent the semigroup using a positive process with three components: an exponential term constructed from the eigenvalue, a martingale, and a transient eigenfunction term. The eigenvalue encodes the risk adjustment, the martingale alters the probability measure to capture long‐run approximation, and the eigenfunction gives the long‐run dependence on the Markov state. We discuss sufficient conditions for the existence and uniqueness of the relevant eigenvalue and eigenfunction. By showing how changes in the stochastic growth components of cash flows induce changes in the corresponding eigenvalues and eigenfunctions, we reveal a long‐run risk‐return trade‐off.     

Event dependent sampling of recurrent events

The effect of event-dependent sampling of processes consisting of recurrent events is investigated when analyzing whether the risk of recurrence increases with event count. We study the situation where processes are selected for study if an event occurs in a certain selection interval. Motivation comes from psychiatric epidemiology where repeated hospital admissions are studied for patients with affective disease, as seen in Kessing et al. (Acta Psychiatr Scand 109:339–344, 2004b). For the selected processes, either only disease course from selection and onwards is used in the analysis, or, both retrospective and prospective disease course histories are used. We examine two methods to correct for the selection depending on which data are used in the analysis. In the first case, the conditional distribution of the process given the pre-selection history is determined. In the second case, an inverse-probability-of-selection weighting scheme is suggested. The ability of the methods to correct for the bias due to selection is investigated with simulations. Furthermore, the methods are applied to affective disease data from a register-based study (Kessing et al. Br J Psychiatry 185:372–377, 2004a) and from a long-term clinical study (Kessing et al. Acta Psychiatr Scand 109:339–344, 2004b).     

Can higher life expectancy induce more schooling and earlier retirement?

In this paper, we show that it may be optimal for individuals to educate more and retire earlier when life expectancy increases. This result reconciles the findings of Hazan (Econometrica 77:1829–1863, 2009) with theory. Further, the paper contributes to a better understanding of the conflicting empirical findings on the causal effect on income per capita from increased life expectancy.