The Corrosive Effect of Corruption on Trust in Politicians: Evidence from a Natural Experiment

Despite the existence of observational studies revealing a negative correlation between corruption and political trust, we lack reliable evidence that isolates the causal effect of corruption on citizens’ trust, especially outside of the lab. In this paper we capitalize on the causal identification advantages generated by the fact that a major Spanish corruption scandal (the Barcenas scandal) was uncovered during the fieldwork of the sixth round of the European Social Survey in Spain. Given that, under certain conditions, the day at which survey interviews were conducted is as if-random, the uncovering of the Barcenas scandal provides an exogenous source of variation in levels of corruption, and represents a unique opportunity to assess the causal impact of a real-world corruption scandal on citizens’ trust in politicians. Our results indicate that the corruption scandal had a substantial negative effect on citizens’ levels of trust in politicians, even if baseline levels of political trust in Spain were already considerably low before the scandal. We also find that there is a decay of the effect over time, since the differences between the treatment and control groups become smaller as we move away from the day the Barcenas scandal was uncovered. Our results also reveal that the impact of the scandal is independent from partisan preferences, since the treatment effect is similar for those who support the party involved in the scandal (PP) and those who do not.