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Essays in Personnel and Development Economics
No full textThe state plays an important role in economic development, and there is growing interest in understanding how government employees, their characteristics, and the institutional context they operate in, affect public goods provision and public service delivery. Governments are also among the largest employers, and their personnel decisions are complex, as they are not directly guided by market forces. Additionally, the diversity of the government workforce itself may influence policy outcomes. U.S. history offers an ideal setting to explore these topics, given its rich historical panel data on government personnel and significant policy variation.In Chapter 1, Socorro Martinez and I study the impact of pay standardization in the US Civil Service on gender equity. Pay standardization schemes are commonly implemented in organizations to address pay gaps based on gender, race, or ethnicity. These schemes limit managerial discretion to determine wages, thereby limiting gender inequality within job titles. However, this may shift inequality to other margins, such as position quality or promotions. This study examines the effects of the Classification Act of 1923, which standardized pay grades and position categories and required "equal pay for equal work" in the US Civil Service, on women's earnings relative to men's. Using a triple difference approach, we exploit the fact that the policy applied to civil servants working in Washington, D.C., but not to those working in federal field offices, and allow for differential effects of the policy by gender. We find that the law did not improve women's relative pay within job titles. Further, the law lowered women's relative compensation without controlling for job titles, suggesting changes in women's positions. We indeed find large negative effects on the position margin. In response to the law, departments downgraded women to lower-quality positions. These negative consequences predominantly affected newly hired women. Our findings underscore the importance of unintended margins of adjustment for policies related to gender equity.Data collection in development economics research is rapidly evolving, driven by new technologies that enable researchers to survey households in different ways and by the increasing availability of administrative data from sources such as satellites and smartphones. Researchers face numerous design decisions when planning data collection for impact evaluations, including sampling strategies, sample size, and questionnaire design. Importantly, the choice of data collection mode may meaningfully influence findings in impact evaluations.In Chapter 2, co-authored with Travis Lybbert, Ashish Shenoy, Rupika Singh, and Daniel Stein and published in the Journal of Development Economics, we measure differences in responses between phone and in-person household agricultural surveys and test for differences in randomized control trial treatment effects by mode of data collection. Ubiquitous mobile phone ownership makes phone surveying an attractive method of low-cost data collection. We explore differences between in-person and phone survey measures of agricultural production collected for an impact evaluation in India. Phone responses have greater mean and variance, a difference that persists even within a subset of respondents that answered the same question over both modes. Treatment effect estimation remains stable across survey mode, but estimates are less precise when using phone data. These patterns are informative for cost and sample size considerations in study design and for aggregating evidence across study sites or time periods.Multi-intervention agricultural development programs are often expensive to implement at scale and sustain over the long term. Therefore, identifying the most cost-effective combination of interventions to achieve program goals is particularly important. This task becomes especially relevant given that policymakers must frequently make decisions under resource constraints, prioritizing interventions that deliver the greatest impact at the lowest cost. In Chapter 3, co-authored with Rupika Singh, Daniel Stein, and Kate Sturla, we measure the cost-effectiveness of different packages of input subsidies and extension interventions, designed to encourage the adoption of modern pulse cultivation. India is the largest producer and consumer of pulses, but in recent years has needed to import pulses to meet domestic demand. In order to keep prices stable and control the balance of trade, increasing domestic pulse production has become a national policy priority. However, farmers face multiple constraints to pulse cultivation.We design an experiment to measure the relative importance of these constraints to design an optimal short-term policy for pulse promotion. We conduct an RCT testing three different implementation models designed to ease different constraints: the "high intensity" provides seed distribution, extension services, and demonstration plots, the "medium intensity" provides seed distribution and extension services, and the "low intensity" only provides seed distribution via a voucher system. Overall, we find that all three models are effective in promoting pulse cultivation, with no statistically significant differences between the models. Treatment increased farmers’ propensity to grow pulses over two seasons by 12 and 15 percentage points, respectively. These results suggest that, at least for the initial phase of pulse adoption, access to quality seeds is the key constraint, as opposed to information. Therefore, seed distribution is likely a cost effective way to quickly increase the adoption and production of pulse crops
Irrigation infrastructure and satellite-measured land cultivation impacts: Evidence from the Senegal river valley
Full text linkExpanding irrigation in sub-Saharan Africa is widely viewed as a promising strategy for closing yield gaps and enhancing resilience to climate change. Drawing on more than 3,000 satellite images over a 30-year period, we examine the impact of irrigation infrastructure development in the Senegal River Valley. We find that cultivation rates increase substantially following irrigation project completion. Cultivation rates are remarkably stable at around 25 percentage points above pre-irrigation levels for the first 20 years, and trend even higher from years 20 to 25. Moreover, we show that crops cultivated on irrigated land are significantly less sensitive to both positive and negative temperature shocks, underscoring the role of irrigation in climate adaptation. Despite these aggregate gains, we document considerable heterogeneity in project outcomes, with intermittent land use remaining widespread. To shed light on these patterns, we complement the satellite analysis with farmer survey data, which point to persistent water access constraints as a key barrier to continuous cultivation—constraints that cannot be resolved solely through individual farmer action
Continuum framework for multiscale contact mechanics of elastic-plastic fractal interfaces with intervening boundary film
Full text linkA comprehensive mechanics theory was developed to analyze multiscale contact and friction behavior of elastic-plastic fractal surfaces coated with a boundary film. This approach accounts for the size-dependent behavior of asperity microcontacts that arise from the inherent roughness of fractal topographies. To capture the fundamental mechanisms governing interfacial friction, representative single-asperity models were formulated to describe both elastic and plastic deformation modes at the microscale. These models were then systematically extended across the entire asperity population, enabling an accurate representation of contact interactions over a broad range of length scales. In the elastic regime, frictional resistance is primarily attributed to shearing of the boundary film between opposing asperities. Conversely, in the plastic regime, asperities indent and plow through the softer counterface material, while the boundary film remains attached to the deformed surface contributing additional resistance through interfacial shear. The total frictional force is obtained by integrating the contributions from both elastic and plastic microcontacts, which are weighted according to the asperity-size distribution that characterizes the fractal contact interface. The developed theoretical framework provides a rigorous and scalable model for predicting the frictional behavior of rough contact interfaces covered by a strongly adhered boundary film and yields fundamental insight into the interplay between surface topography, prevalent deformation mode at the asperity scale, and boundary film shear resistance, which is especially relevant for the design and analysis of engineered surfaces in contact-mode mechanical systems
Full spectrum modeling of in situ gamma-ray detector measurements with a focus on precipitation-induced transients
Full text linkGamma-ray detectors that are deployed outdoors experience increased event rates during precipitation due to the attendant increase in Rn-222 progeny at ground level. The increased radiation due to these decay products (Pb-214 and Bi-214) has been studied for many decades in applications such as atmospheric science and radiation protection. For those applications radon progeny signatures are the signal of interest, while in the fields of radiological and nuclear security and aerial radiological mapping they are a nuisance. When searching for radiological contamination or missing sources, an analyst must take precipitation into account to reduce false alarms, in addition to accounting for static background signatures. To train advanced search algorithms, an effort has been underway to generate synthetic gamma-ray event data that represent a realistic urban area, including occasional rain events to add to the realism. This manuscript describes an effort to analyze and model gamma-ray spectra measured during rainfall by a NaI(Tl) detector located outdoors in order to derive accurate source terms for Pb-214 and Bi-214 at a high frequency (less than 1 min). All known sources of background were quantitatively modeled across the full gamma-ray spectrum, so that the Pb-214 and Bi-214 activity concentrations on the ground could be inferred from a linear model fit to each spectrum. A physically motivated model was applied to the data to further smooth the fits, which had the benefit of yielding information about the concentrations of the progeny in rainwater and their apparent age, making this the first time full-spectrum modeling has been used for continuous measurements of radon progeny. Full-spectrum modeling's ability to leverage more statistics allows for measurements at a rate of more than once per minute, rather than the more typical 10- or 15 min measurement cycle, and therefore this approach could lead to studies of radon progeny on shorter timescales than previously possible
A cost–benefit framework to evaluate capacity upgrade options in overhead line transmission planning
Full text linkThis paper presents the methodology behind the new Reconductoring Economic and Financial Analysis (REFA) tool, an open-access software, used by transmission utilities to evaluate transmission capacity enhancement options. The proposed methodology is intended to be used in a new planning stage, after the capacity expansion and prior to the individual transmission project engineering, allowing capacity upgrade options (reconductoring, rebuild or voltage upgrade), and respective conductor selection, to be compared under the same economic basis. The REFA tool implements a methodology to rank project options and conductor types based on economic criteria, considering an approximation of the ampacity and sag constraints. Results, using 5 real transmission lines in the US, show that least-cost combinations of project and conductor types can be very diverse, which emphasizes the need for the proposed methodology and tool
Effects of intermittent cooling on human thermophysiological and perceptual responses in a non-steady-state thermal environment
Full text linkIntermittent cooling, characterized by the on-off cycling of air-conditioning systems, generates a non-steady-state indoor thermal environment. While widely adopted for energy conservation, its impact on human thermophysiological and perceptual dynamics remains insufficiently understood. To investigate this, we conducted chamber experiments in a simulated residential/office space using three cooling set-points (thermostat target temperature: 28 °C, 26 °C, and 20 °C). Each trial involved 70 minutes of active cooling followed by 50 minutes of shutdown. We continuously monitored indoor air temperature, skin temperature, blood pressure, heart rate, and subjective thermal responses from 12 participants throughout each cycle. Results show that cold exposure intensity significantly shaped the temporal dynamics of human thermal response. Under strong cooling (20 °C), skin temperature declined continuously without stabilization over 70 minutes, thermal sensation and acceptability remained unstable until 35 - 40 minutes, and cardiovascular responses (e.g., DBP, HR) were only activated after prolonged exposure, stabilizing after > 50 minutes. In contrast, moderate and weak cooling (26 - 28 °C) enabled most physiological and perceptual responses to stabilize within 15 - 25 minutes. Asynchronous was observed among systems: skin temperature stabilized earliest, followed by perceptual responses, while cardiovascular regulation remained notably delayed under stronger cooling. After AC shutdown, overall recovery occurred within 35 minutes transitional timeframe, during which the effects of residual cold exposure continued to influence thermal perception and physiology. Based on these findings, we propose a theoretical framework for a “Cumulative Thermal Stimulus (CTSI)” index that integrates thermal deviation and exposure duration, offering a quantitative tool for adaptive cooling strategies that optimize comfort, health, and energy efficiency
Atmospheric drivers of interannual variability from the northern hemisphere seasonal cap on Mars
Full text linkEMERGE patch, a novel electrogenic engineered material to enhance healing of severe corneal wounds
Full text linkSevere corneal wounds with stromal damage, especially those inflicted in battlefield and terrorist attacks, remain a significant clinical challenge. Naturally occurring wound electric fields have been demonstrated to have powerful effects on the healing of corneal epithelial wounds. Here we developed a functional scaffolding material with electrogenic pharmaceutical agents to enhance the healing of stromal wounds, i.e. Engineered Materials that Create Environments for ReGeneration via Electric Field (EMERGE). We first used an excimer laser to produce rat cornea stromal wounds with precisely controlled size and depth and demonstrated that such wounds produced large endogenous wound electric currents. The application of electrogenic compounds significantly increased the wound electric currents and wound healing. We then optimized the EMERGE patches with controlled fibril density, orientation, topography, thickness, optical, and biomechanical properties. The EMERGE patch has the advantage of the way that it supports optimal growth and migration of corneal epithelial cells in vitro. A corneal pocket keratotomy was used to secure the EMERGE patch in deep stroma rabbit corneal wounds without sutures. Corneas were examined with OCT and histological studies for up to four weeks and in one animal up to one year. The EMERGE patch increased wound healing significantly over the non-implant and electrogenic treatment controls (P < 0.05). Optical clarity was significantly improved (P < 0.05), and corneal thickness, histology, and staining of corneal cells showed favorable effects when treated with the EMERGE patch. This novel material thus represents a functional scaffolding with electrogenic agents to enhance the healing of severe corneal wounds
Smartphone location data show park use patterns in extreme heat (Los Angeles, California, USA)
No full textClimate change, combined with the Urban Heat Island effect, will generate more frequent, intense extreme heat events. These events can induce heat stroke, organ damage, and death, especially in lower-income communities, communities of color, and people with chronic health conditions. Research demonstrates parks mitigate extreme heat and combat Urban Heat Island effects locally. To investigate how parks provide heat relief in Los Angeles County, California, we compared park use on extreme heat and control days from the summer of 2017. Our research uses big spatial datasets from smartphone devices to describe broad park use. We intersected anonymous smartphone geolocation data with county parks and census tract layers, then analyzed how the time of day, day of week, and park amenities influenced visitation. Then, we assigned users location-based social sensitivity indices using nighttime locations to explore demographic influence on park use. We found 1) park attendance decreased during extreme heat, 2) temporal convenience, rather than cooling amenities, influenced park use, and 3) users were more likely to visit parks with similar social sensitivity scores as their residence. Our results highlight the influence of social factors above extreme heat on park user behavior. We recommend that city planners focus on equitably and creatively distributing blue and green cooling amenities to communities (i.e. areas of convenience, common daily routes), rather than enhancing parks specifically