Causal inference with generalized structural mean models

Summary.  We estimate cause–effect relationships in empirical research where exposures are not completely controlled, as in observational studies or with patient non-compliance and self-selected treatment switches in randomized clinical trials. Additive and multiplicative structural mean models have proved useful for this but suffer from the classical limitations of linear and log-linear models when accommodating binary data. We propose the generalized structural mean model to overcome these limitations. This is a semiparametric two-stage model which extends the structural mean model to handle non-linear average exposure effects. The first-stage structural model describes the causal effect of received exposure by contrasting the means of observed and potential exposure-free outcomes in exposed subsets of the population. For identification of the structural parameters, a second stage 'nuisance' model is introduced. This takes the form of a classical association model for expected outcomes given observed exposure. Under the model, we derive estimating equations which yield consistent, asymptotically normal and efficient estimators of the structural effects. We examine their robustness to model misspecification and construct robust estimators in the absence of any exposure effect. The double-logistic structural mean model is developed in more detail to estimate the effect of observed exposure on the success of treatment in a randomized controlled blood pressure reduction trial with self-selected non-compliance.     

Modified chain sampling plans for lot inspection by variables and attributes

The purpose of acceptance sampling is to develop decision rules to accept or reject production lots based on sample data. When testing is destructive or expensive, dependent sampling procedures cumulate results from several preceding lots. This chaining of past lot results reduces the required size of the samples. A large part of these procedures only chain past lot results when defects are found in the current sample. However, such selective use of past lot results only achieves a limited reduction of sample sizes. In this article, a modified approach for chaining past lot results is proposed that is less selective in its use of quality history and, as a result, requires a smaller sample size than the one required for commonly used dependent sampling procedures, such as multiple dependent sampling plans and chain sampling plans of Dodge. The proposed plans are applicable for inspection by attributes and inspection by variables. Several properties of their operating characteristic-curves are derived, and search procedures are given to select such modified chain sampling plans by using the two-point method.     

Volunteer Reliability in Nonprofit Organizations: A Theoretical Model

The reliability of volunteers is a major concern for many nonprofit organizations. To address this problem in more detail, we develop a theoretical model of volunteer reliability based on psychological contract theory. By taking this perspective as a starting point, we explore how individual volunteer characteristics, organizational factors, and sociological developments shape the exchange of inducements and contributions between volunteers and nonprofit organizations. We discuss how these factors can create tensions in the psychological contract and determine the extent to which volunteers behave reliably. As such, we develop a theoretical framework for addressing the reliability problem in volunteer management.     

Comparison of causal effect estimators under exposure misclassification

Over the past decades, various principles for causal effect estimation have been proposed, all differing in terms of how they adjust for measured confounders: either via traditional regression adjustment, by adjusting for the expected exposure given those confounders (e.g., the propensity score), or by inversely weighting each subject's data by the likelihood of the observed exposure, given those confounders. When the exposure is measured with error, this raises the question whether these different estimation strategies might be differently affected and whether one of them is to be preferred for that reason. In this article, we investigate this by comparing inverse probability of treatment weighted (IPTW) estimators and doubly robust estimators for the exposure effect in linear marginal structural mean models (MSM) with G-estimators, propensity score (PS) adjusted estimators and ordinary least squares (OLS) estimators for the exposure effect in linear regression models. We find analytically that these estimators are equally affected when exposure misclassification is independent of the confounders, but not otherwise. Simulation studies reveal similar results for time-varying exposures and when the model of interest includes a logistic link.     

Agency Problems between Managers and Employees in Nonprofit Organizations: A Discrete Choice Experiment

Most principal–agent literature of nonprofit organizations has focused on the relationship between board members and managers. However, in addition to the role as an agent of the board, the manager also performs a role as principal with respect to the nonprofit employees. By using a discrete choice experiment, we identify the objectives of managers and employees in nonprofit organizations and assess the presence of agency problems in this relationship. Our sample consists of 76 headmasters, 161 teachers, and 39 administrative employees in 74 secondary nonprofit schools in Belgium. We find that the six objectives set out in the experiment play an important role for both headmasters and subordinate staff. However, the results also indicate that some of these objectives are significantly more important for the headmasters. In sum, our results suggest that agency theory and stewardship theory are not necessarily in conflict with each other but can be combined into a more general governance framework for nonprofit organizations. Consequently, we argue that incentive structures that incorporate different types of objectives can facilitate the recruitment and retention of employees in nonprofit organizations.     

Does it pay to care? Volunteering and employment opportunities

We investigate whether volunteering has a causal effect on individual employment opportunities. To this end, a field experiment is conducted in which volunteering activities are randomly assigned to fictitious job applications sent to genuine vacancies in Belgium. We find that volunteers are 7.3 percentage points more likely to get a positive reaction to their job applications. The volunteering premium is higher for females but invariant with respect to the number of engagements.     

Questioning the professionalization of recovery: a collaborative exploration of a recovery process

While the recovery concept strongly resonates in clinical mental health care today, it first arose in service user-led contexts. A major risk of this professionalization shift is that recovery primarily becomes defined by treatment providers. This study aims to keep the debate on recovery alive through a collaborative exploration of Pete’s recovery process by means of a bricolage approach. This resulted in an idiographic portrait of Pete’s experiences of recovery and treatment, clustered around four themes: life rebuilding, identity, continuity of care and the role of drugs. His experiences illustrate a number of contradictions in the operationalization of the recovery ethos in today’s mental health care; whilst recovery appears as a hopeful vision of empowerment, it also risks being reduced to a tokenistic model that fails to address the social realities of people in recovery and in which the assumption that mental illness is chronic is still latently present.     

Family Support Groups for Family Members of Mentally Ill Offenders: Therapeutic Factors

This study investigates therapeutic factors of a Family Support Group (FSG) intervention for family members of mentally ill offenders. Seventeen family members completed the ‘Group Therapeutic Factors‐Client Questionnaire’ (GTF‐CQ‐28) during four sessions of two FSGs. Results indicate that family members experienced the following therapeutic factors over the course of treatment: the relational climate, interactional confirmation, expressing and experiencing mutual positive feelings, forgetting own problems, hope from seeing progress in others, guidance from therapists, and getting interpersonal feedback treatment. The therapeutic factors, including learning by observation, support from the group, and universality of problems, correlated with a decrease in self‐blame, improved emotional well‐being, and experiencing less loss of control over one's life, respectively. Further, family members were satisfied with what the FSG has provided for them personally and for the relation with their relative. Finally, clinical implications of the FSG are discussed. The study sheds light on valuable therapeutic factors within an FSG and the important role of therapists.     

A Rational Theory of Mutual Funds' Attention Allocation

The question of whether and how mutual fund managers provide valuable services for their clients motivates one of the largest literatures in finance. One candidate explanation is that funds process information about future asset values and use that information to invest in high‐valued assets. But formal theories are scarce because information choice models with many assets are difficult to solve as well as difficult to test. This paper tackles both problems by developing a new attention allocation model that uses the state of the business cycle to predict information choices, which in turn, predict observable patterns of portfolio investments and returns. The predictions about fund portfolios' covariance with payoff shocks, cross‐fund portfolio and return dispersion, and their excess returns are all supported by the data. These findings offer new evidence that some investment managers have skill and that attention is allocated rationally.