Intergroup contact and nation building: Evidence from military service in Spain

•We study the effects of intergroup contact on nation building.•We exploit a national lottery that allocated conscripts to different military areas.•Service outside one's own region has long-run effects on one's national identity.•This result is driven by individuals from regions that have a weak Spanish identity.•We also find a voting behavior that is consistent with the findings on identity. We study the long-term effects of intergroup contact on nation building by exploiting a national lottery that randomly allocated conscripts to different military areas across Spain. For men born in regions that feature a weak Spanish identity, we find that being assigned to military service in a different region substantially increases self-identification as Spanish, increases the likelihood of voting in national elections and reduces the probability of voting for a regionalist party. Moreover, in support of intergroup contact as the main mechanism behind these results, we find that movers are more likely than nonmovers to have friends from other regions.