The author thanks Claudia Goldin, Lawrence Katz, Edward Glaeser, Katherine Coffman, Johanna Rickne, David Ellwood, and participants in the Harvard Graduate Student Workshop in Labor Economics and the Harvard Proseminar on Inequality and Social Policy for helpful comments and suggestions. The author also thank the U.S. Postal Service (USPS) employees who provided valuable information about the institutional details of the USPS.