Nathaniel Mark

Antitrust Division, U.S. Department of Justice 
PhD in Economics, Columbia University

The views expressed here are my own and are not purported to reflect those of the U.S. Department of Justice.


Market Segmentation and Competition in Health Insurance (link), with Kate Ho and Mike Dickstein. Revise and Resubmit, Journal of Political Economy. Available as NBER Working Paper 29406.
In the United States, households obtain health insurance through distinct market segments. We explore the economics of this segmentation by comparing coverage provided through small employers versus the individual marketplace. Using data from Oregon, we find households with group coverage spend 26% less on covered health care than households with individual coverage yet face higher markups. We develop a model of plan choice and health spending to estimate preferences in both markets and evaluate integration policies. In our setting, pooling can both mitigate adverse selection in the individual market and benefit small group households without raising taxpayer costs.

Access to Care in Equilibrium (link).
Abstract:  This paper studies consumer access to medical care as an equilibrium outcome of a market without prices. I use data from the Northern Ontario primary care market to estimate an empirical matching model where patients match with physicians. The market is cleared by a non-price mechanism: the effort it takes to find a physician. I use the model to study the distribution and determinants of access to care and to evaluate the effectiveness of policy remedies. I find that access to care is low and unevenly distributed. 26% of patients who would see a physician in a full access environment do not receive care in 2014. The issue is particularly acute in rural areas. Further, physicians discriminate in favor of patients with higher expected utilization, thereby increasing access for older and sicker patients while decreasing access for younger and healthier patients. The estimated model is used to evaluate two policies: grants to incentivize physicians to practice in low-access areas and a payment reform that provided incentives for physicians to increase the numbers of patients on their books. While both policies are partially successful, the model suggests potential improvements.