Environmental Regulations and Corruption: Automobile Emissions in Mexico City
49 Pages Posted: 15 Aug 2009
Date Written: August, 14 2009
Abstract This paper proposes a methodology for uncovering cheating with emission testing at smog-check facilities in Mexico City. I focus on a widespread form of cheating called emission substitution, which involves testing repeatedly and consecutively a low-emitting vehicle, or donor car, in order to provide low emissions for one or more cheating vehicles. Cheating can be identified because emission readings from the same vehicle have a lower variance than readings from different vehicles. In other words, readings from vehicles that appear to have been tested consecutively are closer than one would expect from random vehicle arrival to the center. This idea is formalized in non-parametric and parametric statistical tests. The results from both tests show that cheating occurs in nearly all centers.
Keywords: cheating, vehicle emissions, smog checks, corruption
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