Theses and Dissertations from UMD
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Item MOSQUITOES AND VEGETATION ACROSS SOCIOECONOMIC GRADIENTS(2024) Rothman, Sarah; Leisnham, Paul T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The biomass and composition of local vegetation is a key resource for juvenile mosquitoes, affecting a suite of life history traits including survival, development rate, and body size. In cities across the United States, both plant and mosquito communities vary with socioeconomics. Vegetation is typically more abundant and biodiverse in high-income neighborhoods, whereas mosquitoes are often more numerous and more likely to vector diseases in low-income neighborhoods. While prior work has examined the effects of plant resources on mosquitoes, my dissertation evaluates how these communities interact across a socioeconomically diverse urban landscape. Chapter 1 is a scoping review of current knowledge of the individual relationships between mosquitoes, plants, and socioeconomics in cities. In Chapter 2, I describe fine-scale vegetation surveys on socioeconomically diverse residential properties in Baltimore, MD and Washington, D.C. that revealed less canopy cover, more vines, and more non-native plant species on lower-income blocks. In Chapter 3, I used leaves from the most frequently observed canopy species on low- and high-income blocks, and species common to both, as detrital resource bases in competition trials between two dominant urban mosquitoes, Aedes albopictus and Culex pipiens. Population performance for both species was greater when reared with characteristically low-income than characteristically high-income detritus, suggesting that socioeconomically diverse plant communities are an important factor in shaping urban mosquito communities. Overall, population performances were greatest when mosquitoes were reared in the regionally representative detritus, and I used this detritus base in Chapter 4 to evaluate the effects of varying temperatures. Aedes albopictus population performance was optimized at higher mean temperatures characteristic of low-income blocks, while C. pipiens performance was best at lower mean temperatures characteristic of high-income blocks. Population performance was often lower, however, when temperatures fluctuated around a high or low mean than when the temperature was stable, suggesting that laboratory studies may need to mimic field conditions to obtain applicable results. My research provides a deeper understanding of the mechanisms behind previously observed relationships, and may help guide management and policy strategies to address environmental injustices and public health threats.Item Income Inequality and Caste in India: Evidence from India Human Development Surveys(2021) Joshi, Omkar; Vanneman, Reeve D; Sociology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The problem of income inequality has become a defining problem in today’s world yet, the implications of overall income inequality for different social groups remain understudied. The sociological literature on stratification has treated these two important facets of inequality, namely overall income inequality and group income gaps, separately. I study these two problems together in this dissertation by examining overall income inequality and caste and religious groups in the context of Indian society. Using the nationally representative data from India Human Development Surveys, I first examine in detail, overall income and consumption changes and inequality from 2004-05 to 2011-12. Then, I look at changes in income and consumption for different caste and religious groups and study inequality changes between these groups. In the end, I evaluate the role played by educational expansion and returns to education in explaining changes in overall income inequality as well as group income gaps using OLS and Quintile regression models.I find that income inequality based on both income as well as consumption measures has increased in India between 2004-05 and 2011-12. But contrary to the global pattern of increasing income inequality, income inequality in India was driven not just because of high growth for households at the top, but more so due to low growth of incomes for households at the bottom of the income distribution. Despite this rise in overall income inequality, income gaps and inequality between the forward caste and disadvantaged caste groups are getting closed. Though caste disadvantage is operational at all parts of income distribution, it becomes less oppressive over time. I find that while education helps explain the declining between-caste income inequality, it does not satisfactorily answer why overall income inequality is growing. I also find that socially disadvantaged groups as well as low educational households who are concentrated disproportionately at lower incomes did better in terms of their income growth over time. Yet, the low-income households as a whole somehow did not grow much over time. These opposite trends among lower income households, is a puzzling result.Item ADOPTION, IMPACT EVALUATION, AND TECHNICAL EFFICIENCY OF IRON BIOFORTIFIED BEAN PRODUCTION IN RWANDA(2020) Funes, Jose Elias; Sun, Laixiang; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Micronutrient malnutrition, also known as hidden hunger, is a public health problem in many developing countries. Hidden hunger limits cognitive and physical development of children and increases both children’s and adults’ susceptibility to infectious diseases. The most common outcome of iron deficiency is anemia and in Rwanda, iron micronutrient malnutrition is highly pervasive. Thirty seven percent of children under five years of age and nearly 20 percent of women of childbearing age suffer from anemia in the country. Since 2012, HarvestPlus and its partners have been intensively disseminating iron biofortified common beans (Phaseolus Vulgaris) (IBB) varieties to help alleviate iron deficiency in Rwanda. On one hand, Rwandan farmers may be uncertain about the economic returns of this new technology owing to insufficient knowledge about the types and costs of inputs needed, the yield distribution, expected market prices, and the demand for the produce. On the other hand, policy makers and donors cannot observe the outcomes that bean farmers would experience under all treatments of the IBB program. The counterfactual outcomes that a bean farming household would have experienced under other treatments are not observable. In this context, this dissertation uses a multiprong analytical framework to: 1) analyze how peer interactions, households and farm characteristics, as well as regional factors influence smallholder farming households’ decisions to grow IBB varieties, 2) evaluate the impact of the IBB program on Rwandan farmer’s livelihoods, focusing on the outcomes of yields and incomes for beneficiary households, and 3) estimate the impact of the IBB program on smallholder farming households’ technical efficiency. The spatial econometric results indicate spatial interdependence in smallholder farming households' decisions to adopt IBB. In addition to the directly targeted beneficiaries, the spatial parameters from the econometric analysis suggest that the biofortification program affected non-beneficiaries as well. This finding indicates that (1) a household is more likely to grow IBB if the household is near other early IBB adopters who informed them about the nutritional and yield benefits of IBB technology and (2) the propensity of a household to grow IBB varies with the characteristics of neighboring farmers. The impact evaluation analysis supports the hypothesis that IBB growers had significantly higher yields and incomes, as compared to farmers that grew non-biofortified beans, whether improved or traditional. In addition, the impact assessment shows that farmers who grew iron biofortified varieties were relatively more efficient and obtained greater bean production than the control group.Item Empirical Essays on Disability Insurance, Employment and Health(2012) Moore, Timothy John; Kearney, Melissa S; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The optimal design of tax and transfer policies involves understanding how income payments affect the behavior of recipients. This dissertation contributes to the public economics literature by examining how various income payments affect employment and health. The first chapter is focused on the relationship between disability payments and employment. The other two chapters explore short-term patterns in mortality and the role of income payments, which advances our understanding of the broader relationship between income and health. Chapter 1: The Employment Effects of Terminating Disability Benefits: Insights from Removing Drug and Alcohol Addictions as Disabling Conditions A challenge in designing return-to-work policies for Social Security Disability Insurance or Supplemental Security Income disability beneficiaries is identifying who is able to work. Using administrative data, I estimate the employment effects resulting from the 1996 removal of drug and alcohol addictions as disabling conditions, which eliminated the benefits of approximately 100,000 individuals. Terminated beneficiaries' employment increased by 20-30 percentage points, which is large relative to their work histories. The heterogeneity in employment is consistent with program participation initially increasing employment potential, before being outweighed by the negative consequences of being out of the labor force. Chapter 2: Liquidity, Economic Activity, and Mortality (with William N. Evans) We document a within-month mortality cycle where deaths decline before the first day of the month and spike after the first. This cycle is present across a wide variety of causes and demographic groups. A similar cycle exists for a range of economic activities, suggesting the mortality cycle may be due to short-term variation in levels of economic activity. Our results suggest a causal pathway whereby liquidity problems reduce activity, which in turn reduces mortality. These relationships may help explain the pro-cyclical nature of mortality. Chapter 3: The Short-term Mortality Consequences of Income Receipt (with William N. Evans) Researchers and retailers have documented that consumption declines before the receipt of income, and then rises afterwards. We identify a related phenomenon, where mortality rises immediately after income receipt. We find that mortality increases following the arrival of monthly Social Security payments, regular wage payments for military personnel, the 2001 tax rebates, and Alaska Permanent Fund dividend payments. The increase in short-run mortality is large, and occurs for a large number of causes of death.Item Applications of Physics to Finance and Economics: Returns, Trading Activity and Income(2005-05-12) Silva, Antonio Christian; Yakovenko, Victor M; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation reports work where physics methods are applied to financial and economical problems. Some material in this thesis is based on $3$ published papers \cite{SY,SPY,income} which divide this study into two parts. The first part studies stock market data (chapter 1 to 5). The second part is devoted to personal income in the USA (chapter 6). We first study the probability distribution of stock returns at mesoscopic time lags (return horizons) ranging from about an hour to about a month. While at shorter microscopic time lags the distribution has power-law tails, for mesoscopic times the bulk of the distribution (more than 99\% of the probability) follows an exponential law. The slope of the exponential function is determined by the variance of returns, which increases proportionally to the time lag. At longer times, the exponential law continuously evolves into Gaussian distribution. The exponential-to-Gaussian crossover is well described by the analytical solution of the Heston model with stochastic volatility. After characterizing the stock returns at mesoscopic time lags, we study the subordination hypothesis with one year of intraday data. We verify that the integrated volatility $V_t$ constructed from the number of trades process can be used as a subordinator for a driftless Brownian motion. This subordination will be able to describe $\approx 85\%$ of the stock returns for intraday time lags that start at $\approx 1$ hour but are shorter than one day (upper time limit is restricted by the short data span of one year). We also show that the Heston model can be constructed by subordinating a Brownian motion with the CIR process. Finally, we show that the CIR process describes well enough the empirical $V_t$ process, such that the corresponding Heston model is able to describe the log-returns $x_t$ process, with approximately the maximum quality that the subordination allows ($80\% - 85\%$). Finally, we study the time evolution of the personal income distribution. We find that the personal income distribution in the USA has a well-defined two-income-class structure. The majority of population (97--99\%) belongs to the lower income class characterized by the exponential Boltzmann-Gibbs (``thermal'') distribution, whereas the higher income class (1--3\% of population) has a Pareto power-law (``superthermal'') distribution. By analyzing income data for 1983--2001, we show that the ``thermal'' part is stationary in time, save for a gradual increase of the effective temperature, whereas the ``superthermal'' tail swells and shrinks following the stock market. We discuss the concept of equilibrium inequality in a society, based on the principle of maximal entropy, and quantitatively show that it applies to the majority of population.