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<p>This thesis deals with the incidence and economic effects of payroll taxes earmarked for unemployment insurance. A major objective is to provide an appropriate theoretical framework for a discussion of this issue. In cases where D.I. coverage is reasonably comprehensive, S6 that the D.I. tax can be regarded as a broad based tax, it is argued that the proper engine of analysis is basically the standard macroeconomic general equilibrium model. The macroeconomic effects of taxation, whether they originate from the demand or supply side, are regarded as an integral part of incidence analysis.</p> <p>The standard macro framework requires modification in one direction, which is a ~ore detailed development of the aggregate labour supply function. This reflects the view that the most important macroeconomic effects of unemployment insurance are likely to emerge from the supply side, via work incentives.</p> <p>A number of variants of a small macroeconomic model are developed, each incorporating an explicit modelling of a hypothetical D.I. system. Qualitative incidence results are obtained using the traditional method of comparative statics, while a quantitative dimension is added in static and dynamic simulation exercises with plausible parameter values drawn from the relevant econometric literature. Different versions of the model employ various alternative hypotheses about the way in which the labour market operates and/or different specifications of the aggregate labour supply function.</p> <p>The incidence results depend largely on the effect of payroll tax increases on labour supply. In the so-called neoclassical version of the model, for example, payroll tax increases reduce both participation and average weeks worked by participants, but tax and benefit rates are connected via the D.I. budget constraint, and benefit rate changes also effect labour supply. An increase in the benefit rate will tend to reduce average weeks worked by participants but to increase participation itself. Therefore a balanced budget increase in payroll tax rates has a potentially ambiguous effect on labour supply. If the net impact on lahour supply is negative we obtain the 'standard' incidence results. A balanced budget increase in payroll tax rates reduces output and emplo)~ent, increases the general price level, and reduces both capital and labour income. (Similar results also occur in other versions of the model in which the labour market does not clear due to (e.g.) real or money wage rigidity.) On the other hand, if the net impact on labour supply is positive we obtain 'perverse' results, increases in output and employment, reductions in the price level and so on.</p> <p>The comparative static analysis and simulation exercises enable us to identify the key parameters in the aggregate labour supply function, and their critical values. For plausible parameter values, chosen on the basis of the available empirical evidence, it would appear that perverse results are not likely. However, there is clearly a need for more empirical investigation in this area.</p> <p>These results conflict with the traditional view that labour bears the full burden of payroll taxation, but we conclude that this view depends heavily on the assumed inelasticity of the aggregate labour supply function. The latter assumption is demonstrated to be inconsistent with the bulk of the empirical evidence on labour supply.</p> <p>Finally, some attention is also paid to the aggregate demand effects of unemployment insurance, in particular the case where the savings propensity out of U.I. benefits is less than that out of private factor incomes.</p> / Doctor of Philosophy (PhD)

Background dependence is a ubiquitous attribute of eukaryotic gene systems that modulates the phenotypic effects of a mutant allele due to segregating genetic variation among different wildtype strains. Despite the wealth of literature demonstrating the presence of genetic background effects, very little is known about how they functionally or mechanistically contribute to the relationship between genetic variation and phenotypic expression. It has been postulated that background dependent effects may be highly specific to the activity of individual alleles or genes. A recent examination of mutant alleles in two interacting genes in the Drosophila wing network demonstrated the magnitude of phenotypic effect of a mutant allele may predict it’s sensitivity to the genetic background. To further understand this, I examined the background dependence of many alleles for genes across the regulatory network of Drosophila wing development in many inbred strains. Our goal was to understand whether effects of the genetic background are an attribute of individual alleles, alleles of the same gene, or genes with similar phenotypes or developmental roles. Our analysis suggests that background dependence is highly positively correlated among alleles of the same gene, especially between alleles with similar magnitudes of phenotypic effect. Similarly, the background dependence of genes within the same regulatory network were also positively correlated. Alleles from different genes, but of the same magnitude of phenotypic effect, generally demonstrated the highest degree of intergenic correlation. However, the background dependence of mutant alleles were generally not well correlated with the wildtype allele. Interestingly, we also found no recovery of any lethal alleles, despite thousands of individuals screened and evident suppression of mutant effects in some strains. We also analyzed the magnitude of intra-line variance in among a subset of our genes. This demonstrated a strong positive relationship between the magnitude of intra-line variation and the severity of phenotypic effects, regardless of the identity of the mutant allele. However, we show no correlation between intra-line variability in the wildtype and the magnitude of perturbation for a given mutant allele. To confirm the quantitative estimates of mean wing size accurately reflected subtle perturbations to wing tissue, we conducted a semi-quantitative analysis and compared it to our quantitative estimates. We demonstrate a high degree of correlation between the quantitative and semi-quantitative approaches, indicating semi-quantitative analysis is a useful way to capture subtle phenotypic effects. In addition, we repeated the quantitative analysis with a subset of the genes and inbred strains from the original data. Importantly, results of the repeated study largely recapitulate our original results. / Thesis / Master of Biological Science (MBioSci)

The early developmental environment has a profound influence on an individual's life history trajectory and parents have tremendous influence over this environment. Despite the wealth of research demonstrating that incubation temperature affects a suite of traits important to fitness in reptiles, we are only now discovering that nest temperatures are a defining component of the avian developmental environment. Aspects of the nest environment may be an important and overlooked maternal effect in birds as nearly all birds physically incubate their eggs, thus providing a clear link between parental behavior and the developmental environment of the avian embryo. My research used an interdisciplinary approach, uniting concepts from life history theory, bioenergetics. immunology, and physiological ecology to investigate the importance of incubation temperature to avian phenotype. I found that incubation temperature affects a suite of traits important for future development, survival and reproduction in a species of birds. Using a population of wood ducks (Aix sponsa) that has been the subject of long term studies I investigated the effects of incubation temperature on embryonic developmental patterns and energy expenditure, and body size and condition, stress endocrinology, thermoregulatory performance, and immunocompetence in hatchling wood ducks. In all experiments freshly laid wood duck eggs were collected from nest boxes located in SC, transported to Virginia Tech and incubated at one of three temperatures (35.0, 35.9, 37.0Ë C) that fell within the range of naturally-incubated wood duck nest temperatures. I found that less than 1Ë C differences in incubation temperature affected duckling growth and body condition, stress endocrinology, immune responses, and energy expended to thermoregulate. Many of these effects persisted days to weeks after hatching. In most cases, ducklings that hatched from eggs incubated at lowest temperature performed poorer than ducklings that hatched from eggs incubated at the higher temperatures. Incubation temperature also affected wood duck embryonic developmental trajectories and energy expended during incubation with embryos from the low incubation temperature expended more energy and developing slower than ducklings incubated at the higher temperatures. Embryonic energy expenditure could contribute to effects observed on hatchling phenotype. Because I demonstrate that incubation temperature affects hatchling phenotypic quality, the variability upon which natural selection acts, my findings have implications for avian ecology, life history evolution and conservation. / Ph. D.