Friday, April 21, 2017 Thomson House, McGill University — Partisanship is increasingly seen as an impediment to cooperation in political settings in the United States given high levels of political polarization. But does partisanship also affect behavior in non-political settings? A field experiment in an online labor market indicates that workers exhibit systematically lower reservation wages when the employer shares their political stance, reflecting a preference to work for co-partisans. A second experiment administered on a large, national classified ads platform over the course of one-and-a-half years shows that consumers, primarily in response to Republican sellers, are more likely to shun (seek) profitable market transactions with sellers affiliated with the opposing (same) party. Via a population-based survey experiment, we find that the influence of political considerations on economic choices is not confined to ardent partisans; rather, it extends throughout the electorate. These negative externalities in the economic domain suggest that partisanship shapes cooperation in everyday behavior.