Essays in macroeconomics and labor economics

This doctoral thesis is made up of three chapters at the intersection between macroeconomics and labor economics, all dealing with topics related to search frictions in the labor market. In the first chapter, I develop a tractable model of firm and worker reallocation over the business cycle that emphasizes the interplay between firms with heterogeneous productivities and on-the-job search. I use this framework to study the role of search frictions in determining aggregate labor productivity following a large economic contraction. In the model, search frictions slow down worker reallocation after a recession, as employed workers face increased competition from a larger pool of unemployed workers. This crowding-out effect holds back the transition of employed workers from less to more productive firms, thus lowering aggregate productivity. Quantitatively, the model implies that worker reallocation has sizable and persistent negative effects on aggregate labor productivity. I provide evidence for this channel from data on the universe of British firms which show that the allocation of workers to firms has downgraded in the aftermath of the Great Recession. In the second chapter, I study the unemployment risks faced by self-employed workers. Though public unemployment insurance (UI) schemes represent an important feature of the social safety net in most advanced economies, the self-employed are generally excluded from these programs. This chapter shows that, similarly to employees on a wage contract, the self-employed do go through unemployment spells in US data. It then calibrates a job search model to evaluate the potential welfare gains from extending UI benefits to this group of workers. The model features workers moving between paid- and self-employment who face the risk of becoming unemployed. Agents can also privately save and borrow to self-insure. My results suggest that extending UI benefits to the self-employed yields modest welfare gains. In the third chapter, I use longitudinal data on patents to quantify sorting in knowledge production. The dimension of sorting I study is that arising between inventors and their ``firm'' (private corporations, universities, public research institutes). My analysis points to the existence of clear, positive inventor-firm sorting. This mechanism accounts on average for five percent of the total variance of inventor output in the US between 1975 and 2010. This framework further suggests that the geographical sorting of inventors and firms is a key channel to explain regional disparities in inventor output

Pathways toward Zero-Carbon Electricity Required for Climate Stabilization

World Bank Policy Research Working Paper 7075This paper covers three policy-relevant aspects of the carbon content of elec-tricity that are well established among integrated assessment models but under-discussed in the policy debate. First, climate stabilization at any level from 2 • C to 3 • C requires electricity to be almost carbon-free by the end of the century. As such, the question for policy makers is not whether to decarbonize electricity but when to do it. Second, decarbonization of electricity is still possible and required if some of the key zero-carbon technologies — such as nuclear power or carbon capture and storage — turn out to be unavailable. Third, progres-sive decarbonization of electricity is part of every country's cost-effective means of contributing to climate stabilization. In addition, this paper provides cost-effective pathways of the carbon content of electricity — computed from the results of AMPERE, a recent integrated assessment model comparison study. These pathways may be used to benchmark existing decarbonization targets, such as those set by the European Energy Roadmap or the Clean Power Plan in the United States, or inform new policies in other countries. These pathways can also be used to assess the desirable uptake rates of electrification technolo-gies, such as electric and plug-in hybrid vehicles, electric stoves and heat pumps, or industrial electric furnaces

Buckling of a spinning elastic cylinder: linear, weakly nonlinear and post-buckling analyses

International audienceAn elastic cylinder spinning about a rigid axis buckles beyond a critical angular velocity, by an instability driven by the centrifugal force. This instability and the competition between the different buckling modes are investigated using analytical calculations in the linear and weakly nonlinear regimes, complemented by numerical simulations in the fully post-buckled regime. The weakly nonlinear analysis is carried out for a generic incompressible hyperelastic material. The key role played by the quadratic term in the expansion of the strain energy density is pointed out: this term has a strong effect on both the nature of the bifurcation, which can switch from supercritical to subcritical, and on the buckling amplitude. Given an arbitrary hyperelastic material, an equivalent shear modulus is proposed, allowing the main features of the instability to be captured by an equivalent neo-Hookean model

Pathways toward zero-carbon electricity required for climate stabilization

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Selection of hexagonal buckling patterns by the elastic Rayleigh-Taylor instability

International audienceWe investigate the non-linear buckling patterns produced by the elastic Rayleigh-Taylor instability in a hyper-elastic slab hanging below a rigid horizontal plane, using a combination of experiments, weakly non-linear expansions and numerical simulations. Our experiments reveal the formation of hexagonal patterns through a discontinuous transition. As the unbuckled state is transversely isotropic, a continuum of linear modes become critical at the first bifurcation load: the critical wavevectors form a circle contained in a horizontal plane. Using a weakly non-linear post-bifurcation expansion, we investigate how these linear modes cooperate to produce buckling patterns: by a mechanism documented in other transversely isotropic structures, three-modes coupling make the unbuckled configuration unstable with respect to hexagonal patterns by a transcritical bifurcation. Stripe and square patterns are solutions of the post-bifurcation expansion as well but they are unstable near the threshold. These analytical results are confirmed and complemented by numerical simulations

Instant fabrication and selection of folded structures using drop impact

A drop impacting a target cutout in a thin polymer film is wrapped by the film in a dynamic sequence involving both capillary forces and inertia. Different 3D structures can be produced from a given target by slightly varying the impact parameters. A simplified model for a nonlinear dynamic Elastica coupled with a drop successfully explains this shape selection and yields detailed quantitative agreement with experiments. This first venture into the largely unexplored dynamics of elastocapillary assemblies opens up the perspective of mass production of 3D packages with individual shape selection