A Swing-State Theorem, with Evidence

74 Pages Posted: 20 Mar 2018 Last revised: 29 Mar 2023

See all articles by Xiangjun Ma

Xiangjun Ma

University of Virginia - College of Arts and Sciences

John McLaren

University of Virginia; NBER

Date Written: March 2018


We study the effects of local partisanship in a model of electoral competition. Voters care about policy, but they also care about the identity of the party in power. These party preferences vary from person to person, but they are also correlated within each state. As a result, most states are biassed toward one party or the other (in popular parlance, most states are either ‘red’ or ‘blue’). We show that, under a large portion of the parameter space, electoral competition leads to maximization of welfare with an extra weight on citizens of the ‘swing state:’ the one that is not biassed toward either party. The theory applies to all areas of policy, but since import tariffs are well-measured they allow a clean test. We show empirically that the US tariff structure is systematically biassed toward industries located in swing states, after controlling for other factors. Our best estimate is that the US political process treats a voter living in a non-swing state as being worth 77% as much as a voter in a swing state. This represents a policy bias orders of magnitude greater than the bias found in studies of protection for sale.

Suggested Citation

Ma, Xiangjun and McLaren, John, A Swing-State Theorem, with Evidence (March 2018). NBER Working Paper No. w24425, Available at SSRN: https://ssrn.com/abstract=3143350

Xiangjun Ma (Contact Author)

University of Virginia - College of Arts and Sciences ( email )

United States

John McLaren

University of Virginia ( email )

P.O. Box 400182
Charlottesville, VA 22904-4182
United States
434-924-3994 (Phone)
434-982-2904 (Fax)


1050 Massachusetts Avenue
Cambridge, MA 02138
United States

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