The impact of a transportation intervention on electoral politics: Evidence from E-ZPass

Connor Jerzak | Brian Libgober

Paper Data .bib

Motivation & Background

This paper tackles the long-standing question of how someone’s economic status influences their political behavior. What would be ideal from the perspective of social science would be to randomize different kinds of people to different levels of wealth in order to estimate the causal effect of wealth on vote choice for president in the United States. However, that kind of experiment is hugely expensive (so not practical at a large scale) and would also be ethnically problematic since the experiment wouldn’t be fair. What we can do is try to approximate that same kind of analysis using a kind of observational analysis known as a natural experiment.

Paper Contributions

We used the introduction of electronic tolling (known as “E-ZPass“) as a vehicle for performing that kind of natural experimental analysis. Before E-ZPass, cars had to wait in long lines in order to pay tolls at a physical booth with human workers inside them. After E-ZPass, car movements through the poll were tracked using electromagnetic transponders, greatly reducing traffic congestion around the tolling areas. In our paper, we show that this 40% or more reduction in traffic correlated with a subsequent rise in housing values in nearby areas, as those places suddenly became much more convenient to live in. We then estimated subsequent effects on vote choice for president in the US presidential election.

We found that support for Republican presidential candidates increased in both aggregating voting data and in individual-level campaign contribution behavior. This finding is in line with political economy theory on how, with an increase in wealth, voters will tend to become more economically conservative (i.e. supporting lower taxes) in order to protect their new affluence from taxes. It’s also worth noting that the president can drive tax policies of particular relevance for homeowners, such as the capital gains tax applying to home sales. We also performed numerous robustness and placebo tests to make sure our results were not driven by other unobserved changes between E-ZPass and similar non-E-ZPass areas.


Connor T. Jerzak, Brian Libgober. The impact of a transportation intervention on electoral politics: Evidence from E-ZPass. Research in Transportation Economics, 2020.
  title={The impact of a transportation intervention on electoral politics: Evidence from E-ZPass},
  author={Jerzak, Connor T. and Brian Libgober},
  journal={Research in Transportation Economics},
[Data][Boston Globe Write-up]

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