Abstract
ABSTRACT This paper investigates how labour-market tightness affects market outcomes if firms use informal, self-enforcing, agreements to motivate workers. We characterise profit-maximising equilibria and show that an increase in the supply of homogeneous workers can increase wages. Moreover, even though all workers are identical in terms of skills or productivity, profit-maximising discrimination equilibria exist. There, a group of majority workers is paid higher wages than a group of minority workers, who may even be completely excluded. Minimum wages can reduce such discrimination and increase employment. We discuss how these results relate to empirical evidence on downward wage rigidity, immigration, the gender pay gap and credentialism.