July 14, 2017

The Peltzman Effect

Filed under: Economics, Government, Health, USA — Tags: , , , — Nicholas @ 05:00

The odd situation where increasing the safety of an activity by adding protective gear is offset by greater risk-taking by the participants:

In the 1960s, the Federal Government — in its infinite wisdom — thought that cars were too unsafe for the general public. In response, it passed automobile safety legislation, requiring that seat belts, padded dashboards, and other safety measures be put in every automobile.

Although well-intended, auto accidents actually increased after the legislation was passed and enforced. Why? As [Professor of Economics Steven E.] Lansburg explains, “the threat of being killed in an accident is a powerful incentive to drive carefully.”

In other words, the high price (certain death from an accident) of an activity (reckless driving) reduced the likelihood of that activity. The safety features reduced the price of reckless driving by making cars safer. For example, seatbelts reduced the likelihood of a driver being hurt if he drove recklessly and got into an accident. Because of this, drivers were more likely to drive recklessly.

The benefit of the policy was that it reduced the number of deaths per accident. The cost of the policy was that it increased the number of accidents, thus canceling the benefit. Or at least, that is the conclusion of University of Chicago’s Sam Peltzman, who found the two effects canceled each other.

His work has led to a theory called “The Peltzman Effect,” also known as risk compensation. Risk compensation says that safety requirements incentivize people to increase risky behavior in response to the lower price of that behavior.

Risk compensation can be applied to almost every behavior involving risk where a choice must be made. Economics tells us that individuals make choices at the margin. This means that the incentive in question may lead the individual to do a little more or a little less of something.


The fact that incentives reduce or increase behavior is an economic law: Landsburg posits that “the literature of economics contains tens of thousands of empirical studies verifying this proposition and not one that convincingly refutes it.” Incentives change the effectiveness of government policy and shape day-to-day life.


  1. I will have to check this Pelzman effect. I have my severe doubts that [reduced injuries with seatbelt use] = [increased injuries due to complacency by drivers using seatbelts]. Accidents affecting belted drivers and passangers who would otherwise be killed are much less deadly than accidents where drivers and passenger don’t use belts. People in the same car suffer different fates depending on whether they use belts. If you listen to the local radio news, you have a lot of non-rigorous evidence that this is true.

    My life was saved by seatbelts. The winter weather was bad and so our driver drove carefully –then black ice turned the road surface into a veritable skating rink. The driver was able to regain control of the car because he was belted in. He told us without the belts he was wearing he could not have
    stopped the car.

    Comment by steve muhlberger — July 14, 2017 @ 09:32

  2. The entry in Wikipedia is pretty skeptical:

    The reduction of predicted benefit from regulations that intend to increase safety is sometimes referred to as the Peltzman effect in recognition of Sam Peltzman, a professor of economics at the University of Chicago Booth School of Business, who published “The Effects of Automobile Safety Regulation” in the Journal of Political Economy in 1975 in which he controversially suggested that “offsets (due to risk compensation) are virtually complete, so that regulation has not decreased highway deaths”.[2] Peltzman claimed to originate this theory in the 1970s but it was used to oppose the requirement of safety equipment on trains in the Nineteenth Century (Adams 1879). A reanalysis of his original data found numerous errors and his model failed to predict fatality rates before regulation (Robertson 1977). According to Peltzman, regulation was at best useless, at worst counterproductive. Peltzman found that the level of risk compensation in response to highway safety regulations was complete in original study. But “Peltzman’s theory does not predict the magnitude of risk compensatory behaviour.” Substantial further empirical work has found that the effect exists in many contexts but generally offsets less than half of the direct effect. In the U.S., motor vehicle fatalities per population declined by more than half from the beginning of regulation in the 1960s through 2012. Vehicle safety standards accounted for most of the reduction augmented by seat belt use laws, changes in the minimum drinking age, and reductions in teen driving (Robertson 2015).

    The Peltzman effect can also result in a redistributing effect where the consequences of risky behaviour are increasingly felt by innocent parties (see moral hazard). By way of example, if a risk-tolerant driver responds to driver-safety interventions, such as compulsory seat belts, crumple zones, ABS etc. by driving faster with less attention, then this can result in increases in injuries and deaths to pedestrians.

    It’s one of those ideas that seems compelling, although the actual data may not fully back it up (I’ve seen enough instances of people taking on riskier behaviour when additional safety equipment is installed).

    Comment by Nicholas — July 14, 2017 @ 10:48

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