The Relative Impact Of Public Information In Shaping Investor Expectations

Empirical studies at the individual level (event studies) and those using more general measures of information and/or aggregate price movements often yield somewhat conflicting results regarding the relative importance of public information.  Employing a more focused methodology that begins with no prior limitations on the number and types of public news announcements that may affect the underlying risk-return relationship, we are able to offer additional insight regarding the relative impact of public information.  We find that approximately two-thirds of the changes can be associated with the arrival of public information.  While, in general, this is a stronger link than previously found, it is a weaker link than expected; leading us to conclude that factors other than public information clearly play an important role.  We also provide new results on the relative importance of different information types, and on correlates (such as firm size) of the effect of information

HIV status and mortality of surgical inpatients in rural Zimbabwe: A retrospective chart review

Background: People living with HIV treated with antiretroviral therapy (ART) are now living longer and thus many are requiring surgical procedures. For healthcare resource planning, it would be helpful to better understand the prevalence of HIV in surgical patients, the types of surgery HIV-positive patients are undergoing and whether HIV status impacts mortality. Objective: The goal of this study was to determine the prevalence of HIV in surgical inpatients and the extent of ART coverage, as well as to assess any differences between HIV-positive and HIV-negative patients in type of surgery undergone and in-hospital mortality at Karanda Mission Hospital, Mount Darwin, Zimbabwe. Method: A 1-year retrospective chart review was undertaken to collect clinical and demographic data for adult (excluding maternity cases) and paediatric surgical inpatients including age, sex, type of surgery, HIV status, CD4+ counts and, if patient was HIV-positive, whether he or she was taking ART. Results and conclusion: Charts for 1510 surgical inpatient stays were reviewed. HIV prevalence among the adults was higher than that in the general population in Zimbabwe in 2016 (23.2% vs. 14.7%). There was no significant difference in inpatient mortality between the HIV-negative group and the HIV-positive group. Within the group of patients with malignancies, people living with HIV were significantly younger than uninfected patients (mean age 50.5 vs. 64.4 years; p < 0.01). There were correlations between HIV and certain malignancies. Thus, in addition to AIDS-defining illnesses, clinicians must be alert to squamous cell carcinoma and oesophageal, anal and penile cancers in HIV-positive patients

On One Parameter Functional Forms for Lorenz Curves

This paper shows that using a one-parameter functional form for the Lorenz curve is equivalent to ranking income distributions based on their Gini indices. Irrespective of the underlying data, the fitted Lorenz curves can never intersect. Circu mstances in which one-parameter Lorenz curves can safely be specified are identified and their policy relevance discussed.

The Conundrum of Low COVID-19 Mortality Burden in sub-Saharan Africa: Myth or Reality?

The burden of coronavirus disease (COVID-19) in sub-Saharan Africa (SSA) has been substantially lower compared to other regions of the world. Extensive morbidity and mortality were not observed among countries in SSA during the first wave of the COVID-19 pandemic. To explain this phenomenon, several hypotheses have been formulated, including the low median age of the population in most SSA countries, lack of long-term care facilities, cross-protection from other local coronaviruses, insufficient testing and reporting resulting in an undercounting of COVID-related deaths, genetic risk factors, or the benefit of early lockdowns that were extensive in many SSA countries. Early lockdowns in SSA have been some of the strictest and resulted in devastating economic and social consequences and increased mortality from other health-related problems including maternal deaths. We review the literature and rationale supporting the various hypotheses that have been put forward to account for relatively low hospitalization and death rates for COVID-19 in SSA. We conclude that the strongest evidence would support the demographic age structure with a very low median age as the primary factor in leading to the low mortality seen in the first wave of the pandemic. The impact of new variants of concern in SSA raises the risk of more severe waves. Nevertheless, furthering the understanding of the underlying explanations for the low morbidity and mortality seen across SSA countries may allow the adoption of unique strategies for limiting the spread of COVID-19 without the need for stringent lockdowns

Man and the Last Great Wilderness: Human Impact on the Deep Sea

The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life – SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO2 and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO2 and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods

Essays in labor supply

Typescript (photocopy).The objectives of this dissertation are to examine (1) static and dynamic labor supply behavior of individuals and (2) the separability of commodities from leisure. While these topics are concerned with labor supply behavior they are even more closely related here since they share (1) a theoretical approach which treats labor supply behavior as an aspect of the theory of demand, (2) the use of individual rather than aggregate data, and (3) the application of experimental techniques to animal subjects to generate the data. Many expositions of labor supply theory point out that the labor supply curve may be backward bending. The question of which utility functions allows the labor supply curve to bend back is of interest because of the quantity of empirical evidence consistent with this shape of the labor supply curve, yet this question has received only limited attention. In this dissertation we examine some of the utility functions which appear in the labor supply literature to determine if they allow the labor supply function be bend back. We test between several of these models using data from an experiment in which pigeons are used as subjects. In addition, we analyze these subjects adjustment to changes in wage rates and non-wage income. The primary purpose of this analysis is to determine if any common pattern of adjustment exists, and to characterize the adjustment process. Some problems with existing models are pointed out. An obvious generalization of the two-good (consumption - leisure) model is to the case where than one consumption good is available. This leads to the question of how changes in labor supply affect the composition of consumption. One effect is through changes in the level of income. In general, changes in the quantity of labor supplied will affect the composition of consumption even if income is constant. This latter effect is absent if commodities are separable from leisure. In the dissertation, we derive three new tests for separability. These tests are independent of the specification of the utility function, that is, the tests do not require the algebraic specification of the utility function. These tests are then implemented using data from an experiment in which rats are used as subjects

Essays in labor supply

Typescript (photocopy).The objectives of this dissertation are to examine (1) static and dynamic labor supply behavior of individuals and (2) the separability of commodities from leisure. While these topics are concerned with labor supply behavior they are even more closely related here since they share (1) a theoretical approach which treats labor supply behavior as an aspect of the theory of demand, (2) the use of individual rather than aggregate data, and (3) the application of experimental techniques to animal subjects to generate the data. Many expositions of labor supply theory point out that the labor supply curve may be backward bending. The question of which utility functions allows the labor supply curve to bend back is of interest because of the quantity of empirical evidence consistent with this shape of the labor supply curve, yet this question has received only limited attention. In this dissertation we examine some of the utility functions which appear in the labor supply literature to determine if they allow the labor supply function be bend back. We test between several of these models using data from an experiment in which pigeons are used as subjects. In addition, we analyze these subjects adjustment to changes in wage rates and non-wage income. The primary purpose of this analysis is to determine if any common pattern of adjustment exists, and to characterize the adjustment process. Some problems with existing models are pointed out. An obvious generalization of the two-good (consumption - leisure) model is to the case where than one consumption good is available. This leads to the question of how changes in labor supply affect the composition of consumption. One effect is through changes in the level of income. In general, changes in the quantity of labor supplied will affect the composition of consumption even if income is constant. This latter effect is absent if commodities are separable from leisure. In the dissertation, we derive three new tests for separability. These tests are independent of the specification of the utility function, that is, the tests do not require the algebraic specification of the utility function. These tests are then implemented using data from an experiment in which rats are used as subjects

The Principal-Agent Model When Agents Can Make Mistakes

This paper examines the principal-agent model when the agent can make a mistake by providing the wrong effort level. How the contract is affected depends on (1) whether mistakes can be positive or negative or are always negative and (2) whether the cost of effort depends on intended effort or actual effort