We study individuals who can choose how to compete with an opponent for one nonzero payoff. They can either nudge themselves into a fair set of rules where they have the same information and actions as their opponent, or into unfair rules where they spy, sabotage or fabricate their opponent's...

We provide the first causal evidence of discrimination against migrants seeking child care. We send emails from fictitious parents to 18, 000 early child care centers across Germany, asking if there is a slot available and how to apply. Randomly varying names to signal migration background, we...