You can’t avoid the law of unintended consequences. It strikes everywhere, even in unlikely places. Take the designated hitter rule in baseball. That’s a rule that allows another player to bat in place of the pitcher. Since pitchers are usually very bad hitters, the rule led to more offense and more scoring. But it also caused some unintended consequences, one of which is that pitchers hit the batters more often (Goff et al. 1997). That’s because pitchers don’t fear retaliation. In the old days, a pitcher who hit a batter would likely get plunked himself when he went up to bat. That’s a pretty powerful deterrent against hitting a batter. The designated hitter means that pitchers are no longer punished for hitting batters, so the outcome is more hit batters. Even professional athletes respond to incentives.
Stephen Dubner and Steven Levitt provide another example in an article for the New York Times (2008). The Endangered Species Act was created to protect the habitat of animals that were in danger of going extinct. It stopped developers from building strip malls or parking lots on land that was being used by a protected species. Now let’s think about what happens when we realize that people respond to incentives. What is punished? Owning land with endangered species. So landowners responded by cutting down trees on their own property in order to drive off the endangered species and prevent their land from being designated a critical habitat in the first place.