Measles: A game of chicken

The student presentations in my intermediate microeconomics class force students to use economic models to help them explain current events. During her presentation, Morgan Erickson used the game theory model of “chicken” to explain the recent measles outbreak. The most interesting part of these presentations is the students’ attempt to reconcile the models’ neat predictions with the real world’s somewhat messy outcomes.

In the stereotypical game of chicken, two drivers get into their cars and drive toward each other at high speeds. A person wins the game if he drives straight and the other player “chickens out” by turning his car to avoid a crash. The driver who drove straight can claim to be macho, while the driver who turned is perceived to be wimpy. To play this game, a driver promises to drive straight, hoping to convince the other player to avoid a crash.

Unfortunately, these promises are not believable since any driver, no matter how macho, will veer to avoid a crash if he believes the other player will drive straight. Because the drivers do not believe each other’s promises, sometimes they both drive straight and catastrophic crashes occur.

The decision of whether to get your children vaccinated for measles is much like the driving contest discussed above. A person’s best outcome depends upon the choice another player makes. For instance, Linda will not feel that she needs to get her kids vaccinated if everyone else is vaccinated. This problem deviates from the stereotypical driving game of chicken because the players do not communicate. Linda has no idea if other people get vaccinations. She has to make a guess.

Without clear communication, some people in Linda’s situation will decide against having their kids vaccinated. These choices will result in measles outbreaks, which is this version of the model’s equivalent to a car crash – the outcome that no one wants.

People do not find out that other people were not getting their children vaccinated until there is a measles outbreak. Linda’s child may be ten years old before the child catches measles and passes the disease onto someone else. In this case, it takes the public 10 years to learn about Linda’s decision to forgo vaccinations for her child. Once there is a well-publicized outbreak, almost everyone will believe others are not getting shots for their kids and they probably will get their children vaccinated on their own. However, as time passes memory of the outbreak will fade and people will begin to think it is safe to skip vaccinations again.

Measles vaccinations are not 100% effective. They are about 97% effective. A person can get the disease even though she received the shot. However, if everyone gets the shots, a 97% effectiveness rate is enough to eradicate the disease.

Currently, every state requires that students get vaccinated. Forty-seven states allow exceptions for religious reasons and 16 states, including Arkansas, allow exceptions due to personal beliefs. State governments should eliminate both of these types of exceptions. I am generally not a big fan of government laws that force people to give up freedom. I cannot justify a law that curtails freedom when other people are unaffected by individual decisions. The measles case is different. Other people are hurt by a person’s decision to forgo vaccinations. Too many lives are lost and too many people get sick to justify the continuation of these exceptions.

Joe McGarrity

Joe McGarrity is a professor of economics at the University of Central Arkansas. Contact him by email at joem@uca.edu.