Ellen Muir
Job Market Candidate

Stanford University
Department of Economics
579 Jane Stanford Way
Stanford, CA 94305

Available for virtual interviews at the upcoming ASSA meeting.

Curriculum Vitae

Microeconomic Theory, Market Design

Expected Graduation Date:
June, 2022

Dissertation Committee:

Paul R. Milgrom (Primary):

Mohammad Akbarpour:

Gabriel Carroll:

Ilya Segal:

Job Market Paper

Contracting and vertical control by a dominant platform (with Z.Y. Kang)
We study a platform that sells productive inputs (such as e-commerce and distribution services) to a fringe of producers in an upstream market, while also selling its own output in the corresponding downstream market. The platform faces a tradeoff: any output that it sells downstream increases competition with the fringe of producers and lowers the downstream price, which in turn reduces demand for the platform's productive inputs and decreases upstream revenue. Adopting a mechanism design approach, we characterize the optimal menu of contracts the platform offers in the upstream market. These contracts involve price discrimination in the form of nonlinear pricing and quantity discounts. If the platform is a monopoly in the upstream market, then we show that the tradeoff always resolves in favor of consumers and at the expense of producers. However, if the platform faces competition in the upstream market, then it has an incentive to undermine this competition by engaging in activities, such as "killer" acquisitions and exclusive dealing, that harm both consumers and producers.

Working Papers

Monopoly pricing, optimal randomization and resale (with S. Loertscher)
Forthcoming, Journal of Political Economy
We provide a parsimonious and unified explanation for randomized selling mechanisms widely used in practice, yet commonly perceived as puzzling. Optimality of randomization in the form of conflation and rationing implies that revenue under market clearing pricing is non-concave. Randomization is implementable via opaque pricing and underpricing. Relative to market clearing pricing, randomization increases the equilibrium quantity and quality of goods sold and, consequently, may increase consumer surplus. For fixed quantities, resale increases consumer surplus. However, resale can decrease the equilibrium quantity and quality of goods sold. Thus, resale prohibition, which always benefits the seller, may also increase consumer surplus.

Optimal market thickness (with S. Loertscher and P. Taylor)
Forthcoming, Journal of Economic Theory
Traders that arrive over time give rise to a dynamic tradeoff between the benefits of increasing gains from trade by accumulating traders and the associated cost of delay due to discounting. We analyze this tradeoff in a dynamic bilateral trade model in which a buyer and seller arrive in each period and draw their types independently from commonly known distributions. With symmetric binary types, the optimal market clearing policy can be implemented with posted prices and ex post budget balance, provided it is optimal to store at least one trader. While optimally thick markets involve storing a small number of traders, their performance is nevertheless close to that of a large market. In particular, irrespective of the type distributions, two-thirds of the gains from increased market thickness can be achieved by storing just one trader.

Wage dispersion, minimum wages and involuntary unemployment: A mechanism design perspective (with S. Loertscher)
Presented by S. Loertscher at NYU Stern, UCLA, the University of Virginia, Universitat Autònoma de Barcelona, Singapore Management University, Hitotsubashi University, Korea University, ALETS and Peking University
Adopting a mechanism design approach, we show that wage dispersion and involuntary unemployment are optimal for a monopsony whenever the cost of procurement under market-clearing wages is not convex at the optimal level of employment. A minimum wage between the lowest equilibrium wage and the market-clearing wage decreases involuntary unemployment and increases employment. Whenever a minimum wage induces wage dispersion and involuntary unemployment, a small increase in that wage increases employment and decreases involuntary unemployment. Absent involuntary unemployment, a small increase in the minimum wage still generically increases employment. Extensions analyze quantity competition, horizontal differentiation, migration and unemployment insurance.

The benefits of market thickness for niche products (with S. Loertscher)
Under submission
We use an independent private values model to analyze the social benefits and costs of monopoly market makers. Calling products niche (mass) if the fraction of agents who trade in a Walrasian market is small (large), we show that for sufficiently niche products a thick market monopoly generates more consumer (producer) surplus per buyer (seller) than ex post efficient bilateral trade. Moreover, relative to bilateral trade, the sorting benefits of thick markets grow unboundedly for increasingly niche products. If bilateral trade offers an outside option to trading with a thick market monopoly, mass products better mitigate the monopoly's market power.


Road to recovery: Managing an epidemic (with S. Loertscher)
Journal of Mathematical Economics [Special Issue on the economics of epidemics and emerging diseases], 93, 2021

A general noncentral hypergeometric distribution (with S. Loertscher and P. Taylor)
Communications in Statistics – Theory and Methods, 46(9):4579–4598, 2017

Approximating the equilibrium quantity traded and welfare in large markets (with K. Borovkov)
Stochastic Models, 33(3):411–429, 2017


The economics of COVID-19 (with S. Loertscher)
Pursuit, 22 July 2020