Explaining the evolution and maintenance of cooperation among unrelated individuals is one of the fundamental problems in biology and the social sciences. Recent experimental evidence suggests that altruistic punishment is an important mechanism to maintain cooperation among humans. In this...

Lying to participants offers an experimenter the enticing prospect ofmaking "others' behaviour" a controlled variable,but is eschewed by experimental economists because it may pollute thepool of subjects. This paper proposes andimplements a new experimental design, the Conditional...

This discussion paper led to a publication in <A href="http://onlinelibrary.wiley.com/doi/10.1111/1467-9442.00182/abstract">'Journal of Economics'</A> 102(1) 23-39.<P>We compare a partners condition where the same small group of subjects plays arepeated public good game to astrangers condition where subjects play this game in changing group formations.Subjects in the partners...</p></a>

The effects of stake size on cooperation and punishment are investigated using a public goods experiment. We find that an increase in stake size does neither significantly affect cooperation nor, interestingly, the level of punishment.

Economic behavior often takes place in groups of small numbers of peopleinteracting with each other (like work teams, neighborhoods, socialnetworks, etc.). Characteristic of such interaction is the development of(affective) interpersonal relationships, or social ties. According tosociologists,...

This discussion paper resulted in a publication in <A href="http://www.sciencedirect.com/science/article/pii/S0166046211001062">'Regional Science and Urban Economics'</A>, 42(1-2), 166-76.<p>This paper analyzes the possibilities to relieve congestion using rewards instead of taxes, as well as combinations of rewards and taxes. The model considers a Vickrey-ADL model of...</p></a>

We present an equilibrium-search model with heterogenous workers whosearch for a job in one of two sectors and who lose part of theirskills during unemployment. We show that an import tariff increasethe wage and the employment prospects in the protected sector. Thisresults in a labor market...

This discussion paper resulted in an article in <I>Journal of Health Economics</I> (2013). Volume 32, issue 6, pages 1180-93.<P> Public providers have no financial incentive to respect their legal obligation to exempt the poor from user fees. Health Equity Funds (HEFs) aim to make exemptions effective by...</p></i>