Abstract:Corruption and corruptibility -due to their illegal and therefore secretive nature -are difficult to be assessed either with traditional tools, such as hard data on criminal convictions or soft data elicited through opinion polls, questionnaires, or case studies. While there seems to be agreement nowadays that corruption does have a negative impact on (foreign) private investment and growth, government revenue and infrastructure, and social equality, and while there seems to be evidence that low economic development, federal structure and short histories of experience with democracy and free trade all favour corruption on the macro-level, it is poorly understood what exactly, on the micro-level, the determinants of corruptibility are and what institutional arrangements could be used to fight (the causes of) corruption. In this article we review a third, complementary mode of investigation of corruption and corruptibility: experiments. We assess their strengths and weaknesses, and identify areas where they could be particularly useful in guiding policy choices -namely in designing incentive-compatible and effective anti-corruption measures in public procurement.

This article reports the results of a multiyear series of economic experiments comparing the two dominant types of legal procedures used in adjudication: (1) the "adversarial" model of party-controlled procedure versus (2) the "inquisitorial" model of judge-controlled procedure. The principal finding is that the relative fact-finding efficiency of the two systems, in terms of both the "revelation" of hidden facts and the "accuracy" of decision, depends significantly upon the information structure. Under a "private" information structure, inquisitorial procedure is relatively more efficient, whereas under a "correlated" information structure, adversarial procedure is relatively more efficient.

This paper studies the enforcement of fines, and, in particular, the effects of simplification and salience nudges on timely payments. In a randomized controlled trial, we add cover letters to 80,000 payment notifications for speeding. The letters increase the salience of the payment deadline, the late penalty, or both. Emphasizing only the deadline is not effective. Stressing the late penalty significantly and persistently increases payment rates. The effect is largest if both parameters are made salient. The most effective treatment yields a net revenue gain that covers approximately 25 percent of the labor costs of the ticket administration personnel. A survey experiment documents how the salience nudges alter prior (mis)perceptions about the communicated parameters. The survey results rationalize the differential effects of the treatments and, together with the evidence from the RCT, offer a broader framework for explaining why certain nudges are effective in some contexts but fail in others.

This paper studies the enforcement of fines. We randomly assign 80,000 speeding tickets to treatments that increase the salience of the payment deadline, late penalties, or both. Stressing the penalties significantly and persistently increases payment rates. Emphasizing only the deadline is not effective. The findings from the RCT are consistent with a survey experiment which documents the treatments' impact on priors about parameters of the compliance problem. Exploiting discontinuous variation in fines, we then document a strong price responsiveness: a 1% increase in the payment obligation induces a 0.23 percentage point decrease in timely compliance. This semi-elasticity suggests that the impact of the salience nudges is equivalent to the effect of a 4-9% reduction in fines.