Three Essays on Incentive Design

We present three distinct works on the subject of incentive design. The first focuses on a fundamental aspect of all principal-agent models, the participation constraint. We endogenise the constraint, allowing the agent to influence his outside option, albeit at some detriment to the project he is contracted to work upon. We compare the optimal contract to the literature on the supposed trade-off between risk and incentives. We find support for the Prendergast (2002) observation of a positive relationship between the two variables and ofer an explanation through the use of said influence activities. The second contribution introduces another principal-agent framework for models with both adverse selection and moral hazard, with the novel inclusion of limited liability. Described in a target-setting environment, the findings are related to and support the use of tenure contracts in academia. This is justified by the fact that pooling equilibria maximise the value to the principal and fully separating equilibria are implemented with non-monotonic wage structures. Finally, in opposition to conventional literature, those of low type make rent gains over and above their reservation utility, while the high types break even. The final chapter studies organisational design and allocation of control. We offer conditions whereby firms would wish to integrate, or profit-share, with another, given varying degrees of control allocation. We show that integration comes at a lower cost for the decision-making firm when control is contractible as opposed to transferable. Also we show that the level of incompatibility between firms, unrelated to financial gain, can affect the integration decision.ESR

Gauging Newton's Law

We derive both Lagrangian and Hamiltonian mechanics as gauge theories of Newtonian mechanics. Systematic development of the distinct symmetries of dynamics and measurement suggest that gauge theory may be motivated as a reconciliation of dynamics with measurement. Applying this principle to Newton's law with the simplest measurement theory leads to Lagrangian mechanics, while use of conformal measurement theory leads to Hamilton's equations.Comment: 44 pages, no figures, LaTe

Impact of incomplete percutaneous revascularization in patients With multivessel coronary artery disease: a systematic review and meta-analysis

Background: Up to half of patients undergoing percutaneous coronary intervention have multivessel coronary artery disease (MVD) with conflicting data regarding optimal revascularization strategy in such patients. This paper assesses the evidence for complete revascularization (CR) versus incomplete revascularization in patients undergoing percutaneous coronary intervention, and its prognostic impact using meta‐analysis. Methods and Results: A search of PubMed, EMBASE, MEDLINE, Current Contents Connect, Google Scholar, Cochrane library, Science Direct, and Web of Science was conducted to identify the association of CR in patients with multivessel coronary artery disease undergoing percutaneous coronary intervention with major adverse cardiac events and mortality. Random‐effects meta‐analysis was used to estimate the odds of adverse outcomes. Meta‐regression analysis was conducted to assess the relationship with continuous variables and outcomes. Thirty‐eight publications that included 156 240 patients were identified. Odds of death (OR 0.69, 95% CI 0.61‐0.78), repeat revascularization (OR 0.60, 95% CI 0.45‐0.80), myocardial infarction (OR 0.64, 95% CI 0.50‐0.81), and major adverse cardiac events (OR 0.63, 95% CI 0.50‐0.79) were significantly lower in the patients who underwent CR. These outcomes were unchanged on subgroup analysis regardless of the definition of CR. Similar findings were recorded when CR was studied in the chronic total occlusion (CTO) subgroup (OR 0.65, 95% CI 0.53‐0.80). A meta‐regression analysis revealed a negative relationship between the OR for mortality and the percentage of CR. Conclusion: CR is associated with reduced risk of mortality and major adverse cardiac events, irrespective of whether an anatomical or a score‐based definition of incomplete revascularization is used, and this magnitude of risk relates to degree of CR. These results have important implications for the interventional management of patients with multivessel coronary artery disease

Reassuring and managing patients with concerns about swine flu: Qualitative interviews with callers to NHS Direct

Abstract Background During the early stages of the 2009 swine flu (influenza H1N1) outbreak, the large majority of patients who contacted the health services about the illness did not have it. In the UK, the NHS Direct telephone service was used by many of these patients. We used qualitative interviews to identify the main reasons why people approached NHS Direct with concerns about swine flu and to identify aspects of their contact which were reassuring, using a framework approach. Methods 33 patients participated in semi-structured interviews. All patients had telephoned NHS Direct between 11 and 14 May with concerns about swine flu and had been assessed as being unlikely to have the illness. Results Reasons for seeking advice about swine flu included: the presence of unexpectedly severe flu-like symptoms; uncertainties about how one can catch swine flu; concern about giving it to others; pressure from friends or employers; and seeking 'peace of mind.' Most participants found speaking to NHS Direct reassuring or useful. Helpful aspects included: having swine flu ruled out; receiving an alternative explanation for symptoms; clarification on how swine flu is transmitted; and the perceived credibility of NHS Direct. No-one reported anything that had increased their anxiety and only one participant subsequently sought additional advice about swine flu from elsewhere. Conclusions Future major incidents involving other forms of chemical, biological or radiological hazards may also cause large numbers of unexposed people to seek health advice. Our data suggest that providing telephone triage and information is helpful in such instances, particularly where advice can be given via a trusted, pre-existing service.</p

Mixing hetero- and homogeneous models in weighted ensembles

The effectiveness of ensembling for improving classification performance is well documented. Broadly speaking, ensemble design can be expressed as a spectrum where at one end a set of heterogeneous classifiers model the same data, and at the other homogeneous models derived from the same classification algorithm are diversified through data manipulation. The cross-validation accuracy weighted probabilistic ensemble is a heterogeneous weighted ensemble scheme that needs reliable estimates of error from its base classifiers. It estimates error through a cross-validation process, and raises the estimates to a power to accentuate differences. We study the effects of maintaining all models trained during cross-validation on the final ensemble's predictive performance, and the base model's and resulting ensembles' variance and robustness across datasets and resamples. We find that augmenting the ensemble through the retention of all models trained provides a consistent and significant improvement, despite reductions in the reliability of the base models' performance estimates