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NBER Working Papers and Publications
|November 2005||Underground Gun Markets|
with Philip J. Cook, Jens Ludwig, Sudhir Venkatesh: w11737
This paper provides an economic analysis of underground gun markets drawing on interviews with gang members, gun dealers, professional thieves, prostitutes, police, public school security guards and teens in the city of Chicago, complemented by results from government surveys of recent arrestees in 22 cities plus administrative data for suicides, homicides, robberies, arrests and confiscated crime guns. We find evidence of considerable frictions in the underground market for guns in Chicago. We argue that these frictions are due primarily to the fact that the underground gun market is both illegal and %u201Cthin%u201D -- the number of buyers, sellers and total transactions is small and relevant information is scarce. Gangs can help overcome these market frictions, but the gang%u2019s econ...
Published: Cook, P. J., J. Ludwig, S.A. Venkatesh, and A.A. Braga. "Underground gun markets." Economic Journal 117 (November, 2007).
|July 1999||Testing for Structural Breaks in the Evaluation of Programs|
with Anne Morrison Piehl, Suzanne J. Cooper, David M. Kennedy: w7226
A standard methodology in program evaluation is to use time series variation to compare pre- and post-program outcomes. However, when the timing of a break in a statistical relationship can be determined only by looking at the data, then the usual distribution of the test statistic which assumes exogenous timing of the break is no longer valid. Tests for parameter instability provide a flexible framework for testing a range of hypotheses commonly posed in program evaluation. These tests help pinpoint the timing of maximal break and provide a valid test of statistical significance. These tests are particularly useful when the start date of the intervention and any effect is unclear and possibly endogenous due to implementation lags. A test of parameter instability is applied to the evalua...
Published: Piehl, Anne Morrison, Suzanne J. Cooper, Anthony A. Braga and David M. Kennedy. "Testing For Structural Breaks In The Evaluation Of Programs," Review of Economics and Statistics, 2003, v85(3,Aug), 550-558. citation courtesy of