Philip Marx

Assistant Professor, LSU

Contact Information

Department of Economics2300 Business Education Complex501 South Quad DriveBaton Rouge, LA 70803



Phone: (615) 973-4610philiplmarx@gmail.com
[CV]

Welcome to my website! I am an Assistant Professor at LSU, with interests in microeconomic and econometric theory. To me these interests are connected in two ways: first, the applications, such as the study of racial discrimination and policing reform, and second, the overarching toolkits (especially optimization). Previously I was a postdoc at Harvard University, and before that I completed my PhD at Northwestern University's Kellogg School of Management. Please don't hesitate to get in touch!

Working Papers

"An Absolute Test of Racial Prejudice" (Accepted, Journal of Law, Economics, and Organization)

Abstract: Disparities along racial and ethnic lines persist across domains. Distinguishing among the possible sources of such disparities matters. This paper introduces an absolute test for identifying prejudice in the presence of statistical discrimination. The key intuition of the test is that each officer's search decisions and search outcomes generate a point on a concave ``return possibility frontier,'' whose slope equals the officer's search cost, or personal standard of evidence for conducting a search. Variation along a return possibility frontier provides information about search costs, and a discrepancy in search costs across drivers of different races constitutes prejudice. The model and test generalize and unify the existing literature, and the test can be partially extended to the setting where officers vary in the quality of their information, or discernment. Higher discernment generates an expansion of the frontier, and a version of the test remains valid for more discerning officers. Empirically, the test finds suggestive evidence of prejudice against Hispanic drivers and of varying discernment among officers of different races and ethnicities. These results are relatively robust to (and not well explained by) officer experience.

"Within Compliers and Beyond: Sharp Bounds in Instrumental Variable Models"

Abstract: This paper derives sharp, analytical bounds on counterfactual outcomes and treatment effects in the canonical instrumental variable model with binary and monotone treatment decisions. These bounds strictly improve over the strongest computational bounds available in the literature. The simultaneous improvement in power and interpretability stems from considering empirical consistency with respect to the distributions of observed data, rather than only observed means, combined with a novel set of methods for harnessing the additional empirical content. A generalized framework allows for the derivation of sharp bounds in a variety of common extensions. As main examples, the paper analytically derives sharp bounds on treatment effects for a common choice-theoretic variant, the extended Roy Model. In addition, the method recovers and extends existing sharp bounds on the average treatment effect where outcomes are bounded, as well as suggesting alternative sets of assumptions for meaningful extrapolation beyond compliers.

"Revenue from Matching Platforms," with James Schummer (Accepted, Theoretical Economics)

Abstract: We consider revenue maximization for one-to-one matching platforms. Heterogeneous agents from two sides of a market use the platform to form pairs, yielding non-transferable value. The platform commits to a stable matching mechanism and a match-contingent fee for each of the two sides. Despite the fact that agents on the “short”' side of the market capture relatively more gross value than those on the long side (when preferences are independently drawn; Ashlagi et al., 2017), we show that the platform does not use relative market sizes to price discriminate across the two sides. The analysis leads to an approximation for the platform's expected revenue through a revenue expression for a constrained serial dictatorship mechanism. The approximation shows that the platform's revenue loss from the stability constraint vanishes in large markets. Finally we demonstrate how two types of correlation in preferences lead to two different directions of price discrimination from the baseline case of independence. These effects are absent in classic models of two-sided markets, demonstrating the importance of considering the interaction of capacity constraints and preference correlation.

Work in Progress

"A Model of Policing the Police," with Roland Fryer

"Judge Score Cards," with Alex Albright

"Increasing Risk: Some Dual Constructions"

"A Dynamic Theory of Political Slant in News Media," with Tom Hamami

Education

Ph.D. , Managerial Economics and Strategy, Kellogg School of Management, Northwestern University, 2012-2017

B.S., Economics, B.S., Mathematics, summa cum laude, Tulane University, 2011