Publications

Abstract Abstract This paper investigates linkage to care following community‐based screening for hepatitis B virus (HBV) in rural Senegal. HBV‐positive participants who completed a biological and clinical examination to assess liver disease and treatment eligibility were referred to a regional hospital (if eligible for treatment), invited to join the Sen‐B research cohort study (adults with detectable viral load) or referred to their local health centre (all others). Logistic regressions were conducted to investigate factors associated with (i) uptake of the scheduled post‐screening examination, and (ii) HBV management initiation. Obstacles to HBV management were identified using thematic analysis of in‐depth patient interviews. Of the 206 HBV‐positive participants, 163 (79.1%) underwent the examination; 47 of the 163 (28.8%) initiated HBV management. Women, people not migrating for >6 months/year, individuals living in households with more agricultural and monetary resources, with other HBV‐positive participants, and beneficiaries of the national cash transfer program, were all more likely to undergo the examination. The likelihood of joining the Sen‐B cohort increased with household monetary resources, but decreased with agricultural resources. Initiation of HBV management in local health centre was higher among participants with a non‐agricultural economic activity. Individuals reported wariness and confusion about HBV management content and rationale at various stages of the care continuum, in particular with respect to venous blood sampling and management without treatment. In conclusion, HBV community‐based test‐and‐treat strategies are feasible, but early loss to follow‐up must be addressed through simplified, affordable management and community support and sensitization.
Keywords Hepatitis B surface antigen, Adjusted odds-ratios, DBS, Dried blood spots, XOF, WHO, World Health Organization, SSA, Sub-Saharan Africa, PwHBV, People living with HBV, IQR, Interquartile range, HDSS, Health and Demographic Surveillance System, HBV, Hepatitis B virus, HBsAg, Confidence interval DBS, CI, Confidence interval, Senegal, Chronic hepatitis B virus HBV infection, Linkage to care, AOR, Adjusted odds-ratios CI, West African franc, Dried blood spots HBsAg, Hepatitis B surface antigen HBV, Hepatitis B virus HDSS, Health and Demographic Surveillance System IQR, Interquartile range pwHBV, People living with HBV sSA, Sub-Saharan Africa WHO, World Health Organization XOF
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Abstract How will structural change unfold beyond the rise of services? Motivated by the observed dynamics within the service sector we propose a model of structural change in which productivity is endogenous and output is produced with two intermediate substitutable capital goods. In the productive sector the accumulation of specialized skills leads to an unbounded increase in TFP, as sector becoming asymptotically dominant. We are then able to recover the increasing shares of workers, the increasing real and nominal shares of the output observed in productive service and IT sectors in the US. Interestingly, the economy follows a growth path converging to a particular level of wealth that depends on the initial price of capital and knowledge. As a consequence, countries with the same fundamentals but lower initial wealth will be characterized by lower asymptotic wealth.
Keywords Two-sector model, Technological knowledge, Constant elasticity ofsubstitution, Non-balanced endogenous growth, Structural change, Kaldor and Kuznets facts
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Abstract Episodes of low natural interest rates, even transitory, pose a challenge to monetary policy, by possibly causing the effective lower bound (ELB) on the policy rate to bind. Those episodes are more likely to occur not only when the natural rate is low on average but also when fluctuations around its average level are large. We study the responsiveness of the natural interest rate to structural aggregate shocks affecting the aggregate supply of and demand for savings. Using a quantitative overlapping-generations model, we trace back this responsiveness to the slopes of aggregate savings supply and demand curves and argue that both curves have likely flattened over the past four decades in the US This implies a greater sensitivity of the natural interest rate to structural shocks affecting the supply of and demand for aggregate savings – making it more likely, all else equal, that it fall into negative territory.
Keywords Natural interest rate, Intertemporal income effects, Overlapping-generations
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Abstract We introduce a new approach to apply the boosted difference of convex functions algorithm (BDCA) for solving non-convex and non-differentiable problems involving difference of two convex functions (DC functions). Supposing the first DC component differentiable and the second one possibly non-differentiable, the main idea of BDCA is to use the point computed by the subproblem of the DC algorithm (DCA) to define a descent direction of the objective from that point, and then a monotone line search starting from it is performed in order to find a new point which decreases the objective function when compared with the point generated by the subproblem of DCA. This procedure improves the performance of the DCA. However, if the first DC component is non-differentiable, then the direction computed by BDCA can be an ascent direction and a monotone line search cannot be performed. Our approach uses a non-monotone line search in the BDCA (nmBDCA) to enable a possible growth in the objective function values controlled by a parameter. Under suitable assumptions, we show that any cluster point of the sequence generated by the nmBDCA is a critical point of the problem under consideration and provides some iteration-complexity bounds. Furthermore, if the first DC component is differentiable, we present different iteration-complexity bounds and prove the full convergence of the sequence under the Kurdyka–Łojasiewicz property of the objective function. Some numerical experiments show that the nmBDCA outperforms the DCA, such as its monotone version.
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Abstract We show that the development of abstract reasoning and cognitive empathy (theory of mind) is severely hindered when children are deprived of the stimulation of a school environment. We document significantly lower abstract reasoning and cognitive empathy scores in elementary school children who returned from an extended school closure caused by the Covid-19 pandemic relative to proximate pre-pandemic cohorts. This developmental delay has a significant socioeconomic gradient, with underprivileged children experiencing more substantial delays. We also document a significant disruption in the development of socioemotional skills: 0.24 sd lower grit, 0.43 sd lower emotional empathy, 0.06 sd lower epistemic curiosity, and 0.24 sd higher impulsivity. About eight months of school exposure results in a remarkable recovery in abstract reasoning and theory of mind for all socioeconomic groups. However, the measured levels still indicate significant delays relative to the expected developmental trajectories. No notable improvements are observed in socioemotional skills except for curiosity. These findings reveal that the damage school closures inflicted on children goes beyond well-documented academic losses and highlight the crucial role of the school environment in fostering fundamental cognition and socioemotional development in children.
Keywords Abstract reasoning, Cognitive empathy, Socioemotional skills, Schoolclosures
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Abstract Several factors can deeply affect employees’ quality of life at work. Work-life balance, subjective well-being and job satisfaction are three of these factors and it is in the best interest of companies to handle these topics carefully. This is a sine qua non condition of the strength and the quality of relationships with employees. It is also a source of confidence for employees, especially where this is being mediated through Human Resource (HR) processes. Our article studies the quality of life at work in the particular context of an MAR healthcare pathway that exacerbates the consequences for employees. Our work with hundreds of people enduring an MAR process shows that depending on whether firms take this situation into account or not, employees will feel either well-being or ill-being and will have different burnout or job satisfaction levels. All these variables influence their commitment and job performance. These links between a healthcare pathway and quality of life at work on the one hand, and between the quality of work and performance on the other hand, should lead employers to support employees in a personal vulnerable situation. The strength and the quality of the support provided by the HR function and the management is therefore a key point in the level of confidence that exists between firms and their employees.
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Abstract Over the years, oil prices and financial stock markets have always had a complex relationship. This paper analyzes the interactions and co-movements between the oil market (WTI crude oil) and two major stock markets in Europe and the US (the Euro Stoxx 50 and the SP500) for the period from 1990 to 2023. For that, I use both the time-varying and the Markov copula models. The latter one represents an extension of the former one, where the constant term of the dynamic dependence parameter is driven by a hidden two-state first-order Markov chain. It is also called the dynamic regime-switching (RS) copula model. To estimate the model, I use the inference function for margins (IFM) method together with Kim's filter for the Markov switching process. The marginals of the returns are modeled by the GARCH and GAS models. Empirical results show that the RS copula model seems adequate to measure and evaluate the time-varying and non-linear dependence structure. Two persistent regimes of high and low dependency have been detected. There was a jump in the co-movements of both pairs during high regimes associated with instability and crises. In addition, the extreme dependence between crude oil and US/European stock markets is time-varying but also asymmetric, as indicated by the SJC copula. The correlation in the lower tail is higher than that in the upper. Hence, oil and stock returns are more closely joined and tend to co-move more closely together in bullish periods than in bearish periods. Finally, the dependence between WTI crude oil and the SP500 stock index seems to be more affected by exogenous shocks and instability than the oil and European stock markets.
Keywords Oil and stock markets, GARCH models, Dependence, Regime switching, Dynamic copula
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Abstract Many people obtain job information from friends and acquaintances. However, one factor influencing labor-market outcomes that is ignored in the literature is the presence of overlapping friendship circles in social networks. We find that overlapping friendship networks produce correlated information flows, resulting in an increased probability of two events: either receiving redundant job offers or receiving no job offers at all. Consequently, people with common contact networks exhibit worse employment prospects even if they have the same number of information providers and compete with the same number of people for vacancies. In quantitative terms, the impact of overlapping friendship circles rivals that of the number of direct contacts and contacts’ contacts. This implies that the results in Calvó-Armengol (2004) only apply for networks where people’s friends are neither connected nor have common contacts. Because overlapping friendship circles are a crucial aspect of strong relationships, our findings uncover an alternative mechanism behind "The Strength of Weak Ties" (Granovetter, 1973): their ability to maintain independence in job information flows. We further show that people with common job contacts earn lower incomes on average. However, conditional on being employed, their expected wage is higher because they can take advantage of the multiple job offers received by selecting the one with the highest pay.
Keywords Clustering, Social reinforcement, Information transmission, Employment, Labor, Networks
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Abstract During the medieval and early modern periods the Middle East lost its economic advantage relative to the West. Recent explanations of this historical phenomenon—called the Long Divergence—focus on these regions’ distinct political economy choices regarding religious legitimacy and limited governance. We study these features in a political economy model of the interactions between rulers, secular and clerical elites, and civil society. The model induces a joint evolution of culture and political institutions converging to one of two distinct stationary states: a religious and a secular regime. We then map qualitatively parameters and initial conditions characterizing the West and the Middle East into the implied model dynamics to show that they are consistent with the Long Divergence as well as with several key stylized political and economic facts. Most notably, this mapping suggests non-monotonic political economy dynamics in both regions, in terms of legitimacy and limited governance, which indeed characterize their history.
Keywords Legitimacy, Political economy, Religion, Institutions, Cultural transmission, Long divergence
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Abstract This paper develops a theoretical framework to think about employees' effort choices, and applies this framework to assess the ability of existing experimental designs to identify the effect of pay inequality on worker effort. The analysis shows that failure to control for a number of confounds—such as reciprocity towards the employer in multi-lateral gift-exchange games (vertical fairness), or the incentive to increase effort when feeling underpaid under piece rates (income targeting)—may lead to inaccurate interpretation of evidence of treatment effects. In light of these findings, the paper provides a set of recommendations on how to improve identification in the design of controlled experiments in the future.
Keywords Reference dependence, Laboratory experiments, Fairness, Effort, Pay inequality
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Abstract A common thread in the literature shows that an oil price shock can have a major impact on global economic conditions. We examine the global dimensions of changes to the global oil price and world economic uncertainty using three model types: ordinary least square (OLS); general additive model (GAM); and non-linear vector autoregression (VAR) model with local projections (LP). Our study highlights a positive and statistically significant effect of oil prices on economic uncertainty during non-expansionary periods, yet the impact is negative on economic uncertainty during periods of economic growth. Using a VAR-LP we analyze the global dimensions of a world oil price shock on global economic conditions and investigate whether there is consistency in how an oil price shock influences economic growth, consumer prices and economic uncertainty based on the state of economic conditions. The empirical evidence shows that during an expansionary (a non-expansionary) period, the impact of an oil price shock lowers (elevates) economic uncertainty. The empirical evidence from the three model types taken together indicate a presence of state dependence on the influence of an oil price shock.
Keywords Oil prices, Business Cycles, World Economic Uncertainty
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Abstract We use data from Pakistan to establish a reciprocal exchange relationship between the judiciary and the government. We document large transfers in the form of expensive real estate from the government to the judiciary, and reciprocation in the form of pro-government rulings from the judiciary to the government. Our estimates indicate that the allocation of houses to judges increases pro-government rulings and reduces decisions on case merits. The allocation also incurs a cumulative cost of 0.03% of GDP to the government. However, it allows the government to expropriate additional land worth 0.2% of GDP in one year.
Keywords Reciprocation, Corruption, Pakistan, Judges, Law
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Abstract In an analysis applying automated segmentation to UK Biobank MRI scans, hypertension, higher body mass index, and higher physical activity level were associated with increased left ventricular trabeculations in healthy middle-aged White adults.
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Abstract Given that poor individuals face worse survival conditions than non-poor individuals, one can expect that a steeper income gradient in mortality leads, through stronger income-based selection, to a lower poverty rate at the old age (i.e. the "missing poor" hypothesis). This paper uses U.S. state-level data on poverty at age 65+ and life expectancy by income levels to provide an empirical test of the missing poor hypothesis. Using average temperature as an instrument for mortality differentials, we show that instrumented changes in mortality differentials have a negative and statistically significant effect on old-age poverty: a 1 % increase in the mortality differential implies a 16 % decrease in the 65+ headcount poverty rate. Using those regression results, we compute hypothetical old-age poverty rates while neutralizing the impact of the income gradient in mortality, and show that correcting for heterogeneity in income-based selection effects modifies the comparison of old-age poverty prevalence across states.
Keywords Poverty, Measurement, Income gradient in mortality, Selection biases, Comparability
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Abstract In statistics, samples are drawn from a population in a data‐generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence‐generating process (EGP). We claim that EGP variation across researchers adds uncertainty—nonstandard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for more reproducible or higher rated research. Adding peer‐review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants.
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Abstract We expand the theory of politician quality in electoral democracies with citizen candidates by supposing that performance while in office sends a signal to the voters about the politician’s valence. Individuals live two periods and decide to become candidates when young, trading off against type-specific private wages. The valence signal increases the reelection chances of high valence incumbents (screening mechanism of reelection), and thus their expected gain from running for office (self-selection mechanism). Since self-selection improves the average quality of challengers, voters become more demanding when evaluating the incumbent’s performance. This complementarity between the self-selection and the screening mechanisms may lead to multiple equilibria. We show that more difficult and/or less variable political jobs increase the politicians’ quality. Conversely, societies with more wage inequality have lower quality polities. We also show that incumbency advantage blurs the screening mechanism by giving incumbents an upper-hand in electoral competition and may wipe out the positive effect of the screening mechanism on the quality of the polity.
Keywords Endogenous candidates, Political accountability, Incumbency advantage
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Abstract Purpose The blue and green firms are notable contributors to sustainable development. Similar to other businesses in circular economies, blue and green firms also face financing constraints. This paper aims to assess whether blue and green lending help in optimizing the interest rate spreads and the likelihood of default. Design/methodology/approach This analysis is based on an unbalanced panel of banks from 20 eurozone countries for eleven years between 2012 and 2022. The key indicators of banking include interest rate spread and a market-based probability of default. The paper assesses how these indicators are influenced by exposure to green and blue firms after controlling for several exogenous factors. Findings The results show a positive relationship between green and blue lending and spread, while there is a negative link with the probability of default. This confirms that the blue and green exposure positively supports the credit portfolio both in terms of profitability and risk management. Originality/value The banking system is among the key contributors to corporate finance and to enable continuous access to sustainable finance, the banking firms must be incentivized. While many studies analyze the impact of green lending, to the best of the authors’ knowledge, this study is among the very few that extend this analysis to blue economy firms
Keywords Blue economy, Green lending, Credit portfolios, Probability of default
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Abstract We present an overview of selected contributions of the Journal of Mathematical Economics’ authors to growth theory in the last half century. We start with the classical optimal growth theory within a benchmark multisector model and outline the successive developments in the analysis of this model, including the turnpike theory. Different refinements of the benchmark are considered along the way. We then survey the abundant literature on endogenous fluctuations in two-sector models. We conclude with two strong trends in the recent growth literature: green growth and infinite-dimensional growth models.
Keywords Growth theory, Multisector models, Turnpike theory, Green growth, Infinite dimensional growth models, Optimization
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Abstract div>We study a simple model in which two vertically differentiated firms compete in prices and mass advertising on an initially uninformed market. Consumers differ in their preference for quality.There is an upper bound on prices since consumers cannot spend more on the good than a fixed amount (say, their income). Depending on this income and on the ratio between the advertising cost and quality differential (relative advertising cost), either there is no equilibrium in pure strategies or there exists one of the following three types: (1) an interior equilibrium, where both firms have positive natural markets and charge prices lower than the consumer's income; (2) a constrained interior equilibrium, where both firms have positive natural markets, and the high-quality firm charges the consumer's income or (3) a corner equilibrium, where the low-quality firm has no natural market selling only to uninformed customers. We show that no corner equilibrium exists in which the high-quality firm would have a null natural market. At an equilibrium (whenever there exists one), the high-quality firm always advertises more, charges a higher price and makes a higher profit than the low-quality one. As the relative advertising cost goes to infinity, prices become equal and the advertising intensities converge to zero as well as the profits. Finally, the advertising intensities are, at least globally, increasing with the quality differential. Finally, in all cases, as the advertising parameter cost increases unboundedly, both prices converge increasingly towards the consumer's income.
Keywords Vertical differentiation, Advertising cost, Random advertising
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