Publications

Résumé Les entreprises françaises vont sortir de la crise le dos au mur avec un taux d’endettement de 86 %, proche du double de celui des entreprises allemandes (45 %) et même supérieur à celui des...
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Résumé Using a new and original database, our paper contributes to the growth accounting literature by singling out the contribution of robots through two channels: capital deepening and TFP. The contribution of robots to productivity growth through capital deepening and TFP appears to have been significant in Germany and Japan in the sub-period 1975–1995 and in several Eastern European countries in 2005–2019. However, robotization does not appear to be the source of a significant revival in productivity.
Mots clés Robots, Productivity, Growth
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Résumé There is an urgent need to measure the impacts of COVID-19 among gay men and other men who have sex with men (MSM). We conducted a cross-sectional survey with a global sample of gay men and other MSM (n = 2732) from April 16, 2020 to May 4, 2020, through a social networking app. We characterized the economic, mental health, HIV prevention and HIV treatment impacts of COVID-19 and the COVID-19 response, and examined whether sub-groups of our study population are disproportionately impacted by COVID-19. Many gay men and other MSM not only reported economic and mental health consequences, but also interruptions to HIV prevention and testing, and HIV care and treatment services. These consequences were significantly greater among people living with HIV, racial/ethnic minorities, immigrants, sex workers, and socio-economically disadvantaged groups. These findings highlight the urgent need to mitigate the negative impacts of COVID-19 among gay men and other MSM.
Mots clés Men who have sex with men, Gay, AIDS, HIV, Mental health, Economic impact, COVID-19
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Résumé We investigate how variations in soil productivity affect civil conflicts. We first present a model with heterogeneous land in which variations in input prices (fertilizers) affect appropriable rents and the opportunity costs of fighting. The theory predicts that spikes in input prices increase the likelihood of conicts through their effect on income and inequality, and that this effect is magni fied when soil fertility is naturally more heterogenous. We test these predictions using data on conict events covering all Sub-Saharan African countries at a spatial resolution of 0.5 x 0.5 degree latitude and longitude over the 1997-2013 period. We combine information on soil characteristics and worldwide variations in fertilizer prices to identify local exogenous changes in input costs. As predicted, variations in soil productivity triggered by variations in fertilizer prices are positively associated with conicts, especially in cells where land endowments are more heterogeneous. In addition, we find that the distribution of land fertility both within and across ethnic groups affects violence, and that the effect of between-group heterogeneity in soil quality is magnified in densely populated areas. Overall, our findings imply that inequality in access to fertile areas { an issue largely neglected in the literature dealing with the roots of Sub-Saharan African civil wars { constitutes a serious threat to peace at the local-level.
Mots clés Inequality, Fertility, Land, Conflict
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Résumé The distinction between effort and other factors, such as family background, matters for correcting policies and normative reasons when we appeal to inequality of opportunity. We take advantage of a purposefully designed survey on secondary schools in rural Bangladesh to offer a comprehensive view of the importance of overall effort when measuring inequalities of opportunity in education. The analysis comprises decomposition exercises of the predicted variance of student performance in mathematics and English by source (effort, circumstances, etc.) and subgroup (within- and between-schools) based on parametric estimates of educational production functions. Pupils’ effort, preferences, and talents contribute between 31% and 40% of the total predicted variances in performance scores. The contribution of overall effort falls by 10% when the correlation between effort and circumstances is taken into account. These findings are robust to the choice of estimation strategy (i.e. combined within- and between-schools variation models versus multilevel random-effect models). All in all, these results advocate that social determinism in education can be mitigated by individual effort at school.
Mots clés School, Variance decomposition, Effort, Education, Inequality of opportunity
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Résumé This paper looks at situations in which public and private protection are complementary, that is, when private protection must be coordinated with public protection to be effective. For example, home alarms deter theft by being connected to a local police station: if the police do not respond to a home alarm, the home alarm on its own is virtually useless in halting a crime in action. We make a distinction between gross and net complementarity and substitution, where the latter takes into account the effect on the crime rate. We show that when public and private protection are complements, the optimal provision of public protection trades off the manipulation effect of encouraging private protection with the compensatory effect of providing protection to households that do not privately invest. We discuss the implications of our results for policy and empirical research in this area.
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Résumé We establish an equivalence between three criteria for comparing dis- tributions of an ordinal variable taking finitely many values. The first criterion is the possibility of going from one distribution to the other by a finite sequence of increments and/or Hammond transfers. The latter transfers are like the Pigou-Dalton ones, but without the requirement that the amount transferred be fixed. The second criterion is the unanimity of all comparisons of the distributions performed by a class of additively separable social evaluation functions. The third criterion is a new statis- tical test based on a weighted recursion of the cumulative distribution. We also identify an exact test for the possibility of going from one dis- tribution to another by a finite sequence of Hammond transfers only. An illustration of the usefulness of our approach for evaluating distributions of self-reported happiness level is also provided
Mots clés Inequality, Ordinal, Transfers, Dominance, Distributions
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Résumé This article establishes an equivalence between four incomplete rankings of distributions of income among agents who are vertically differentiated with respect to some nonincome characteristic (health, household size, etc.). The first ranking is the possibility of going from one distribution to the other by a finite sequence of income transfers from richer and more highly ranked agents to poorer and less highly ranked ones. The second ranking is the unanimity among utilitarian planners who assume that agents' marginal utility of income is decreasing with respect to both income and the source of vertical differentiation. The third ranking is the Bourguignon (Journal of Econometrics, 42 (1989), 67–80) Ordered Poverty Gap dominance criterion. The fourth ranking is a new dominance criterion based on cumulative lowest incomes.
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Résumé Market-oriented housing reforms and the rapid urbanization process have led to spectacular growth in the Chinese real estate sector (RES). However, the changes in the role played by this sector in the structural dynamics of the Chinese economy have not been examined sufficiently. Accordingly, we analyze the intersectoral structural changes to the Chinese RES, its linkages with the rest of the economy, and its growth sources, using four Chinese input–output tables from 2002 to 2017. We depart from existing work on the RES by using the causative matrix approach and structural decomposition analysis, and obtain three main results. First, the RES, which received little non-RES feedback during the 2002–2007 period, has subsequently received much more substantial feedback. Second, the impact of the RES on China's economic growth stems mainly from its forward linkages. Third, the growth in the RES has been driven mainly by domestic demand expansion. Our results highlight that the Chinese RES, which plays a key role in value chains, is highly dependent on its own final demand and a fall in its demand would impede economic development. An important implication of these results is that developing the national economy by stimulating the RES would not be as effective as developing the RES through stimulating the national economy.
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Résumé A monopoly sells a network good to a large population of consumers. We explore how the monopoly's profit and the consumer surplus vary with the arrival of public information about the network structure. The analysis reveals that, under homogeneous preferences for the good, degree assortativity ensures that information arrival increases both profit and consumer surplus. In contrast, heterogeneous preferences for the good can create a tension between consumer surplus and profit.
Mots clés Monopoly, Network effects, Network information, Bonacich centrality, Degree assortativity, Assortative mixing
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Résumé In this paper, we consider an abstract optimal control problem with state constraint. The methodology relies on the employment of the classical dynamic programming tool considered in the infinite dimensional context. We are able to identify a closed-form solution to the induced Hamilton-Jacobi-Bellman (HJB) equation in infinite dimension and to prove a verification theorem, also providing the optimal control in closed loop form. The abstract problem can be seen an abstract formulation of a PDE optimal control problem and is motivated by an economic application in the context of continuous spatiotemporal growth models with capital diusion, where a social planner chooses the optimal location of economic activity across space by maximization of an utilitarian social welfare function. From the economic point of view, we generalize previous works by considering a continuum of social welfare functions ranging from Benthamite to Millian functions. We prove that the Benthamite case is the unique case for which the optimal stationary detrended consumption spatial distribution is uniform. Interestingly enough, we also find that as the social welfare function gets closer to the Millian case, the optimal spatiotemporal dynamics amplify the typical neoclassical dilution population size effect, even in the long-run.
Mots clés PDE, PARTIAL DIFFERENTIAL EQUATION, IMPERFECT ALTRUISM, MILLIAN SOCIAL WELFARE FUNCTION, BENTHAMITE SOCIAL WELFARE FUNCTION, SPATIOTEMPORAL GROWTH MODEL, HAMILTON-JACOBI-BELLMAN EQUATION, INFINITE DIMENSION
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Résumé The COVID-19 pandemic has led many governments to implement lockdowns. While lockdowns may help to contain the spread of the virus, they may result in substantial damage to population well-being. We use Google Trends data to test whether the lockdowns implemented in Europe and America led to changes in well-being related topic search terms. Using differences-in-differences and a regression discontinuity design to evaluate the causal effects of lockdown, we find a substantial increase in the search intensity for boredom in Europe and the US. We also found a significant increase in searches for loneliness, worry and sadness, while searches for stress, suicide and divorce on the contrary fell. Our results suggest that people's mental health may have been severely affected by the lockdown.
Mots clés Boredom, COVID-19, Lockdown, Loneliness, Well-being
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Résumé This study explores whether an oath to honesty can reduce both shirking and lying among crowd-sourced internet workers. Using a classic coin-flip experiment, we first confirm that a substantial majority of Mechanical Turk workers both shirk and lie when reporting the number of heads flipped. We then demonstrate that lying can be reduced by first asking each worker to swear voluntarily on his or her honor to tell the truth in subsequent economic decisions. Even in this online, purely anonymous environment, the oath significantly reduced the percent of subjects telling “big” lies (by roughly 27%), but did not affect shirking. We also explore whether a truth-telling oath can be used as a screening device if implemented after decisions have been made. Conditional on flipping response, MTurk shirkers and workers who lied were significantly less likely to agree to an ex-post honesty oath. Our results suggest oaths may help elicit more truthful behavior, even in online crowd-sourced environments
Mots clés Experimental economics, Honesty, Solemn Oath, Mechanical Turk, Lying, Shirking
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Résumé We assess the role of demand noise (excessive optimism or pessimism about demand) together with supply noise (excessive optimism or pessimism about supply). To do so, we propose a methodology to decompose business cycles into supply, demand, supply noise and demand noise shocks, using a structural vector autoregression model. Key to our identification of both supply noise and demand noise is the use of sign restrictions on survey expectation errors about output growth and about inflation. We show that demand-related noise shocks have a negative effect on output and contribute substantially to its fluctuations. Monetary policy and private information seem to play a key role in the transmission of demand noise shocks.
Mots clés SVAR with sign restriction, Noise shock, Information friction, Business cycle
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Résumé This paper discusses the theoretical choice of exchange rate regimes in Sub-Saharan African countries that are facing external vulnerabilities. To reduce instability, policymakers choose among promoting external competitiveness using a real anchor, lowering the burden of foreign debt using a nominal anchor or using a policy mix of both anchors. We observe that these countries tend to adopt mixed anchor policies. We solve a state space model to explain the determinants of and the strategy behind this policy. We find that the mixed targeting policy is a two-step strategy: First, monetary authorities choose the degree of nominal exchange rate flexibility according to the velocity of money, trade openness, foreign debt, degree of exchange rate pass-through and exchange rate target zone. Second, authorities seek to stabilize the real exchange rate depending on the degree of competition in the domestic goods market and the degree of foreign exchange intervention. We conclude with regime-switching estimations to provide empirical evidence of how these economic fundamentals influence exchange rate policy in Sub-Saharan Africa.
Mots clés Regime-switching model, External vulnerabilities, Exchange rate policy, Sub-Saharan Africa
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Résumé We study the joint determination of optimal investment and optimal depollution in a spatiotemporal framework where pollution is transboundary. Pollution is controlled at a global level. The regulator internalizes that: (i) production generates pollution, which is bad for the wellbeing of population, and that (ii) pollution flows across space driven by a diffusion process. We solve analytically for the optimal investment and depollution spatiotemporal paths and characterize the optimal long-term spatial distribution when relevant. We finally explore numerically the variety of optimal spatial distributions obtained using a core/periphery model where the core differs from the periphery either in terms of input productivity, depollution efficiency, environmental awareness or self-cleaning capacity of nature. We also compare the distributions with and without diffusion. Key aspects in the optimal policy of the regulator are the role of aversion to inequality, notably leading to smoothing consumption across locations, and the control of diffusive pollution adding another smoothing engine.
Mots clés Pollution control, Geography, Infinite dimensional optimal control problems, Decision analysis, Transboundary pollution
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Résumé Beta coefficients are the cornerstone of asset pricing theory in the CAPM and multiple factor models. This chapter proposes a review of different time series models used to estimate static and time-varying betas, and a comparison on real data. The analysis is performed on the USA and developed Europe REIT markets over the period 2009–2019 via a two-factor model. We evaluate the performance of the different techniques in terms of in-sample estimates as well as through an out-of-sample tracking exercise. Results show that dynamic models clearly outperform static models and that both the state space and autoregressive conditional beta models outperform the other methods.
Mots clés Autoregressive conditional beta, Dynamic conditional beta, State space, Multivariate GARCH, REITs, Real estate
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