1,721,019 research outputs found
Controlling Mixed-Protein Adsorption Layers on Colloidal Alumina Particles by Tailoring Carboxyl and Hydroxyl Surface Group Densities
No full textWe show that different ratios of bovine serum albumin (BSA) and lysozyme (LSZ) can be achieved in a mixed protein adsorption layer by tailoring the amounts of carboxyl (-COOH) and aluminum hydroxyl (AlOH) groups on colloidal alumina particles (d(50) approximate to 180 nm). The particles are surface-functionalized with -COOH groups, and the resultant surface chemistry, including the remaining AlOH groups, is characterized and quantified using elemental analysis, zeta potential measurements, acid base titration, IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic light scattering. BSA and LSZ are subsequently added to the particle suspensions, and protein adsorption is monitored by in situ zeta potential measurements while being quantified by UV spectroscopy and gel electrophoresis. A comparison of single-component and sequential protein adsorption reveals that BSA and LSZ have specific adsorption sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs only via -COOH groups (1-2 -COOH groups on the particle surface is enough to bind one LSZ molecule). Tailoring such groups on the particle surface allows control of the composition of a mixed BSA and LSZ adsorption layer. The results provide further insight into how particle surface chemistry affects the composition of protein adsorption layers on colloidal particles and is valuable for the design of such particles for biotechnological and biomedical applications
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Essays in Development Economics
Full text linkThis dissertation examines how market failures in low-income countries contribute to low firm and worker productivity, and interact with psychological biases. Chapter I of this dissertation, joint with Luisa Cefala, Pedro Naso and Michel Ndayikeza, investigates the existence of a missing market for training in general human capital, and measures the distortions that arise from this market being missing. In low-income countries, contracts in labor markets are often short-term. Because of this, employers might underinvest in training workers in productivity enhancing general skills because the fact that there is weak labor market attachments mean they cannot guarantee that after training the worker they will capture returns from the training. We conduct two field experiments with agricultural employers in Burundi who can train casual laborers in improved, labor-intensive, agricultural techniques. In the first experiment, we offer employers in some local labor markets (villages) incentives to train workers and show that this generates sizable labor market spillovers. In the second experiment, we show that making it less likely that workers separate after training makes empoyers more likely to train. Chapter II of this dissertation explores the implications of other missing markets on employers' decisions of who to hire in their business. The modal firm in low- and middle-income countries has no employees that are not family members. While this is often attributed to informational or contractual frictions, an alternate view is that pressure to offer financial assistance to extended family in the form of employment may distort employers' hiring decisions. In this chapter field experiments with employers in Zambia to test whether pressure impacts firm hiring and examine its productivity implications. A sample of urban firms are offered the chance to receive a 3-month subsidy for hiring a full-time permanent employee. A subset of firms is then randomized to receive plausible deniability in their hiring decision: receiving a poster that suggests the firm may not have been eligible for the subsidy if it hired a relative. This increases the probability of choosing to hire a non-related employee, rather than a related one. In the second experiment, I show that it is socially very costly for employers to hire a non-relative: when they have plausible deniability, the subsidy required to get a firm to choose a non-relative rather than a relative falls substantially. Finally, I show that in a common agricultural job where productivity is measurable - maize shelling - the same worker is more likely to shirk when working for a related employer. These findings suggest that social pressure to hire relatives may distort the composition of employment as well as productivity in developing countries. Chapter III of this dissertation, joint with Ned Augenblick, Kelsey Jack, Supreet Kaur and Felix Masiye, investigates how limited recourse to credit markets and low savings in low-income savings interacts with psychological biases of savers. In this chapter, we propose that individuals may fail to recall and use information they already know when making decisions. We empirically investigate whether such ``retrieval failures'' distort consumption smoothing behavior among Zambian farmers, who derive their income from one annual harvest and then spend it down over the course of the year. We document that individuals underestimate upcoming spending. In order to improve recall, we randomize an intervention that prompts individuals to think through their future expenses associatively in categories---without providing any external information or guidance. Treated individuals increase ``remembered'' expenses, immediate spending drops and, two months after the intervention, treated households hold higher savings
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Essays on Personnel Economics in Low-Income Countries
Full text linkA key question in personnel economics is how best to motivate and incentivize workers. In this dissertation, I investigate how different incentive systems affect workers' effort and decision on where to work. Rewarding different aspects of workers' performance may allow firms to prioritize certain outcomes and may attract and retain different types of employees who are more or less drawn to particular contracts. Finally, certain incentive schemes may benefit or harm certain sub-groups of employees, especially when there is subjectivity introduced into the evaluation scheme.In the first chapter, joint with Tahir Andrabi, we study whether performance incentives lead to sorting of teachers. Attracting and retaining high-quality teachers has a large social benefit, but it is challenging for schools to identify good teachers ex-ante. We use teachers' contract choices and a randomized controlled trial of performance pay with 7,000 teachers in 243 private schools in Pakistan to study whether performance pay affects the composition of teachers. Consistent with adverse selection models, we find that performance pay induces positive sorting: both among teachers with higher latent ability and among those with a more elastic effort response to incentives. Teachers also have better information about these dimensions of type than their principals. Using two additional treatments, we show effects are more pronounced among teachers with better information about their quality and teachers with lower switching costs. Accounting for these sorting effects, the total effect of performance pay on test scores is twice as large as the direct effect on the existing stock of teachers, suggesting that analyses that ignore sorting effects may substantially understate the effects of performance pay.In the second chapter, joint with Tahir Andrabi, we investigate how different types of incentive pay affect employee behavior. A central challenge facing schools is how to incentivize teachers. While high-powered incentives can motivate effort, they can lead teachers to distort effort away from non-incentivized outcomes. This is one reason why most performance incentives allow for manager subjectivity. However, this subjectivity can introduce new concerns, including favoritism and bias. We study the effect of subjective versus objective performance incentives on teacher productivity using the same randomized controlled trial discussed in chapter 1. We estimate the effect of two performance raise treatments versus a control condition, in which all teachers receive the same raise. The first treatment arm is a "subjective" raise, in which principals evaluate teachers; the second treatment arm an "objective" raise based on student test scores. First, we show that both subjective and objective incentives are equally effective at increasing test scores. However, objective incentives decrease student socio-emotional development. Second, we show that these effects are likely driven by the types of behavior change we observe from teachers during classroom observations. In objective schools, teachers spend more time on test preparation and use more punitive discipline, whereas, in subjective schools, pedagogy improves. Finally, we investigate the mechanisms of these effects through the lens of a moral hazard model with multi-tasking. We exploit variation within each treatment to isolate the causal effect of contract noisiness and distortion on student outcomes. We then show that teachers perceive subjective incentives as less noisy and less distorted, and these contract features affect student outcomes, serving as key channels to explain the reduced form effects we see.Finally, in the third chapter, I explore whether managers show gender bias in their evaluation of employees, and, if so, under what circumstances. Pakistan ranks in the lowest decile in female labor force participation, and even in sectors where women are more prevalent, such as teaching, they earn 70 cents for each dollar men earn. In this chapter, I test the extent to which statistical versus financial discrimination explains these pay gaps. I use the experiment from chapter 1 and 2, which has two important random variations: i). how often managers observe a given employee and ii). whether manager evaluations affect employee's pay or are just used for feedback and see whether this changes how managers evaluate their employees. I find that managers have less gender bias the more frequently they observe a given employee and more gender bias if there is a financial stake of the manager's evaluation. While all three chapters use the same randomization design and data, each chapter is intended to be a stand-alone set of research questions, so the respective design and data description is included within each chapter
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Essays in Development and Behavioral Economics
Full text linkThis dissertation includes four essays at the intersection of development and behavioral economics. A unifying theme across these essays is the exploration of how social environments shape economic decision making. A variety of research methods are employed throughout, including implementing field experiments in real-world contexts, leveraging naturally occurring experiments using administrative datasets, and synthesizing interdisciplinary literature across psychology and economics. Of particular interest is how these dynamics affect low-income and marginalized populations, from manufacturing workers in Tanzania, to the psychology of those living in poverty, to marginalized social and political identities.The first chapter, “Selection and Sorting when Supervisors have Discretion,” coauthored with Yihong Huang, begins from the observation that firms are social organizations. In particular, the relationships between workers and their supervisors are an important part of how employees experience their day to day jobs. These relationships can enhance firm productivity, such as through improved information and trust. Yet, these relationships can also lead to biases and preferential treatment. In practice, almost all firms rely on supervisors to select and motivate workers. But what are the benefits and costs of doing so?To make progress on these questions, we partner with a large garment manufacturing firm in Tanzania to implement a series of field experiments to examine decision making when supervisors have discretion. In particular, we focus on a challenge common to all large organizations: how to select future leaders. In a first field experiment, supervisors are asked to refer workers for promotion to new managerial positions. During the referral process, we randomize whether supervisors face financial incentives based on the quality of their referrals. In a complementary experiment, workers decide whether to apply for the new managerial openings. During the application process, we randomly vary whether supervisor selection is emphasized on the application forms that workers receive.Our results show that discretion crowds in supervisors’ private information about the managerial quality of workers. Supervisors use private information beyond what the firm could infer from existing administrative data, workers’ self-assessments, or coworker referrals. However, discretion also generates costs for firms. Supervisor referrals are not perfectly aligned with the firm’s objectives, and supervisors show preferences consistent with gender bias and favoritism. Furthermore, discretion is disliked by workers and reduces the likelihood that workers apply for promotion, directly reducing the number of high quality candidates that the firm receives. Despite the costs of discretion, supervisors select workers with significantly higher measured managerial ability relative to more objective selection methods. Taken together, the results suggest that firms face meaningful trade-offs in using subjective methods, which select workers with higher managerial quality, against more objective methods, which are transparent and preferred by workers.The exploration of the social dynamics within firms extends to social interactions more generally, particularly the importance of implicit norms. In the second chapter, “Breaking the Spiral of Silence,” also coauthored with Yihong Huang, we explore how social norms and limited attention jointly interact to shape political discourse. We study this in the context of self-censorship on college campuses, where there are both strong social norms governing political expression and where free ideological debate is believed to be critical for learning and innovation.Using a dynamic model and field experiment with UC Berkeley college students, we first establish that social norms shape public discourse on college campuses. Students who hold socially appropriate views are more likely to express their views publicly. In contrast, students who hold socially inappropriate views are more likely to self-censor. This pattern of public expression leads other students to increase their beliefs about the popularity of the socially appropriate views, which further discourages the expression of opposing views, creating a self-fulfilling cycle. Next, we find that inattention to silence is a key mechanism that perpetuates such a spiral and enables misperceptions to persist. When we experimentally increase attention to the number of students who stay silent on a topic, students form more accurate beliefs about the true level of dissent and become more likely to voice dissent to others. With sufficient attention to silence, the spiral of silence is broken and misperceptions are corrected. Extensions using data from real public forums and nationally representative surveys suggest our findings apply not only to college campuses but to political discourse more broadly. Taken together, these results have implications for any decision-making process that either explicitly or implicitly takes public opinion into account. We have been invited to revise and resubmit this chapter for publication at the Journal of Political Economy.Social interactions are governed not only by implicit norms but also by relative comparisons. People inevitably rank themselves against others. When are such comparisons beneficial and when are they harmful? Estimating the effects of relative rank on outcomes poses an empirical challenge because rank is often endogenously determined. In the third chapter “Gender Differences in Competition: The Role of Rank effects” I exploit quasi-exogenous variation in relative rank in a high-stakes, real world setting to study the causal effects of rank on performance. In competitive swimming, swimmers are usually divided into sub-groups, or heats, based on their ex-ante rankings. The difference in entry times between any two swimmers ex-ante is quite small, often tenths of seconds, but swimmers just above the threshold will be placed in a faster heat, as the last ranked swimmer, while swimmers just below the threshold will be placed in a slower heat, as the first ranked swimmer. Exploiting this quasi-exogenous variation in relative rank, I use a regression discontinuity design to estimate the causal effects of rank on performance.Standard economic models would predict no effect of group rank on performance in this setting, as it is rank in the overall competition rather than rank in a specific heat that matters for tournament outcomes. In contrast, the results show there are significant gender differences in response to rank. Women significantly improve their performance when they are ranked first in a slower heat relative to when they are ranked last in a faster heat, whereas there is no comparable effect of rank on performance for men. Taken together, the results suggest there are significant gender differences in response to competition incentives in a real-world, high stakes setting.Across these essays, I seek to understand both how an individual’s circumstances shape their psychology and how their psychology in turn shapes their decisions and their circumstances. In the final chapter, “The Psychology of Poverty: Current and Future Directions,” coauthored with Ye Rang Park, Kristina Hallez, Supreet Kaur, Mahesh Srinivasan, and Jiaying Zhao, we synthesize evidence across both psychology and economics on the psychological impacts of poverty and their potential role in perpetuating poverty. We do so using an organizing framework comprising four sets of mechanisms: cognitive function, mental health, beliefs, and preferences. We discuss the strength of the evidence supporting both how poverty affects these four mechanisms, and how these four mechanisms in turn affect poverty. From our synthesis, we determine that the existing evidence has clearly established proof of concept that psychological factors exist in the experience of and response to poverty. However, there is still a lack of evidence on whether these effects are meaningful in magnitude and lead to the perpetuation of poverty. From our review, we identify promising future directions for research which could help close these evidence gaps, with important implications for the design of poverty reduction policies. This chapter was published in Current Directions in Psychological Science in December 2024.Taken together, these essays highlight the myriad ways in which social identities and social contexts shape economic behavior. Better understanding these patterns helps us to form more accurate models of human behavior, with implications for how to effectively design policies ranging from workplace incentives to poverty reduction programs. There is much that we do not understand about the interplay between social psychology and economics, and what a gift it is to seek the answers
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Essays in Development and Behavioral Economics
No full textThis dissertation examines barriers to financial stability and human capital accumulation faced by low-income workers across different institutional contexts. A significant challenge that low-income workers, both in poor and rich countries, face is the prevalence of income instability--caused, for instance, by irregular labor demand, or frequent shocks to the ability to work. Chapter I examines the welfare effects of providing low-income, credit-constrained workers with access to short-term liquidity. The motivation is that consumption smoothing maybe hard for households experiencing frequent variation in income and expenses. Even when there are no changes in long-term income perspectives, they face periods in which their income is temporarily lower. In these cases, access to liquidity--by transferring resources from a state with low to one with high marginal utility of consumption--would enhance welfare. However, this is not necessarily the case if households have wrong beliefs about their liquidity needs or their income-generating process, or if they suffer from lapses of self-control problems. We partner with a company providing Earned Wage Access services (EWA), \textit{i.e.} the possibility to withdraw part of their income already earned ahead of the pay date, to study workers' demand for liquidity and whether they exhibit signs of self-control when doing so. Motivated by the evidence that workers in this setting exhibit a substantial variation in income from one pay period to another, which could potentially make the prediction of future resources and liquidity needs more difficult, we also ask whether workers mispredict their future income, and how that affects use and forecasts of demand for liquidity.\\We do so through a survey and an experiment with users of our partner's EWA App. From the administrative data, we find evidence of an insurance motive for using the App: when users work less than their average in a given pay period, resulting in lower liquidity on their next pay date, they end up using EWA more in the next pay period. Building on the \citet{allcott2022high} methodology, we then document that users under-predict their demand for EWA (future liquidity) by a substantial amount, and they are willing to pay for an incentive to reduce their future use, consistent with agents' being partially sophisticated about their present focus. We also find that users' demand for incentives to reduce future use depends on their current financial circumstances--when users make predictions in a state with temporarily lower income, they demand less commitment and they under-predict their use by a smaller amount. We interpret this as evidence that users correctly interpret the trade-off between flexibility and commitment that EWA provides. It also implies that the welfare effect of restrictions depends on the prevalence and utility costs of temporarily lower income. We also find a role for over-prediction in income affecting the misprediction in EWA use.Another consequence of volatile work availability --ubiquitous in low-income countries where many workers are employed in seasonal occupations or in informal labor markets-- is that it prevents long-term skill accumulation. We study this phenomenon in Chapter II with respect to a particular skill: the ability to supply labor reliably. We posit that labor supply is not a function of stable preferences for leisure, but rather is also determined by one's past habituation to work. In existing data, we show that exogenously induced transitory changes in labor supply increase supply in subsequent days---indicating that the inter-temporal labor supply elasticity can actually be positive, rather than negative. To examine this phenomenon in more detail, we undertake a field experiment with casual urban stand workers in Chennai, India, where appearance at the stand in the morning provides a revealed preference measure of labor supply. We randomly provide some workers incentives for attending the stand in the morning in a timely manner for two months (phase 1), and examine persistence after incentives are removed for another two months (phase 2). We find that an increase in labor supply in phase 1 generates a persistent 16\% increase in supply in phase 2---leading to a 22\% increase in employment found at the stand. These findings have relevance for understanding the reasons for irregular work attendance and high worker turnover in formal firms, which impede the transition to formal work in this setting. They also suggest that the effects of unemployment spells may go beyond the income loss: unemployment itself can lower a worker's productivity--offering a potential justification for the ``unemployment scar'' phenomenon discussed extensively in the labor literature, whereby employers prefer not to hire workers out of unemployment.In Chapter III, we examine the aspect of human capital accumulation of low-income workers from another perspective, namely employers' incentive to train workers in general skills. There is a long-lasting theory in Economics that general skills may be under-provided in equilibrium due to a failure of those who train to sufficiently appropriate the returns of training \citep{Becker2009}. We provide evidence for this theory in the context of new agricultural technologies in Sub-Saharan Africa. We develop a test tightly linked to theory to assess whether concerns over the appropriability of returns to training generate a socially inefficient level of training, limiting the adoption of new technologies. We conduct two exercises to answer this question. First, we document that the level of training may be socially inefficient. We show that inducing employers to train laborers generates externalities, specifically whether employers uninvolved in training subsequently hired these trained workers and adopted more improved technology in their fields.
We find evidence for such an externality: in villages with trained workers, not only the trainers but also other farmers uninvolved in training hire more skilled labor. We then test whether allowing farmers to appropriate the returns of this training increases training in equilibrium. In a second treatment arm, we randomize farmers to receive a contract that guarantees them the appropriability of returns from their training. Offering labor insurance to the employer- trainers increase the propensity to train substantially. Moreover, this training is consequential and does not appear to be just driven by demand effects. Overall, we find that, in both arms, adoption of the technology increases, suggesting that lack of skilled labor can be a constraint to technology take-up. We also find substantial benefits accruing to trained laborers, both in terms of labor market earnings and profits on their own land. This suggests that under-provision of training can be consequential for skill growth and earning trajectories of poor workers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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