Object-Based Unawareness

The goal of this paper is to construct a user-friendly model of unawareness. We start from an axiom system (in first-order modal logic) that enables us to express the following kinds of sentences: “the agent is not sure whether or not there is anything that he is unaware of”, and “I am not sure whether or not you are aware of something that I am not”. We then prove a characterization theorem which describes a class of structures, called object-based unawareness structures, that correspond to this axiom system. As an application, we explain how an object-based unawareness structure can be use to model those American founding fathers who were opposed to the inclusion of the Bill of Rights in the constitution.unawareness, object-based, modal logic, bill of rights

A non-differentiable approach to revenue equivalence

We give a sufficient condition on the type space for revenue equivalence when the set of social alternatives consists of probability distributions over a finite set. Types are identified with real-valued functions that assign valuations to elements of this finite set, and the type space is equipped with the Euclidean topology. Our sufficient condition is stronger than connectedness but weaker than smooth arcwise connectedness. Our result generalizes all existing revenue equivalence theorems when the set of social alternatives consists of probability distributions over a finite set. When the set of social alternatives is finite, we provide a necessary and sufficient condition. This condition is similar to, but slightly weaker than, connectedness.Revenue equivalence, mechanism design, incentive compatibility, non-differentiable approach, connected type space

Mechanism design with tacit collusion

In the mechanism design literature, collusion is often modelled as agents signing side contracts. This modelling approach is in turn implicitly justified by some unspecified repeated-interaction story. In this paper, we first second-guess what kind of repeated-interaction story these side-contract theorists (would admit that they) are having in mind. We then show that, within this repeated-interaction story, there is a big difference between communicative and tacit collusion. While communicative collusion hurts the mechanism designer, tacit collusion is exploitable

Object-based unawareness: Theory and applications

In this paper and its companion paper, Board and Chung (2021), we provide foundations for a model of unawareness that can be used to distinguish between what an agent is unaware of and what she simply does not know. At an informal level, this distinction plays a key role in a number of recent papers such as Tirole (2009) and Chung and Fortnow (2007). Here we provide a set-theoretic (i.e., non-linguistic) version of our framework. We use our object-based unawareness structures to investigate two applications. The first application provides a justification for the contra proferentem doctrine of contract interpretation, under which ambiguous terms in a contract are construed against the drafter. Our second application examines speculative trade

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe