Incentives Matter

Who do you think gets stuck in the mud or snow more often - people with 4-wheel drive vehicles or those with 2-wheel drive vehicles? Probably those with 4-wheel drive vehicles, right?

Feeling more powerful and invincible with a 4-wheel drive vehicle, drivers are more likely to go off-road or take additional risks and chances in the snow or mud that they would never take with a regular vehicle. Although 4-wheel drive vehicles are less likely to get stuck because of the additional power, the drivers of 4-wheel drive vehicles often take more risks and chances and are more likely to get stuck. Depending on which effect is stronger, drivers of 4-wheel drive vehicles might be more likely, less likely or equally likely to get stuck as drivers of regular vehicles.

Likewise, who do you think gets in more fatal car accidents - drivers wearing seatbelts, or those not wearing seatbelts? Well, it depends, because there are two opposite and offseting effects of wearing seatbelts, just like there are offsetting effects of 4-wheel vehicles:

1) people wearing seatbelts are more likely to survive a serious car accidents; but
2) people wearing seatbelts are also more likely to drive more aggressively and recklessly (like those drivers with 4-wheel drive) and will take more risks and chances when driving.

If Effect #1 is stronger, mandatory seatbelt laws will reduce fatal car accidents. If Effect #2 is stronger, mandatory seatbelt laws will increase fatal car accidents. If Effect #1 and Effect #2 are equal, seatbelt laws will have no effect on fatal car accidents.

From a Time Magazine article (mentioned in the Freakonomics blog) titled "The Hidden Danger of Seat Belts:"

"John Adams, risk expert and professor at University College London, was an early skeptic of the seat belt safety mantra. Adams first began to look at the numbers more than 25 years ago. What he found was that contrary to conventional wisdom, mandating the use of seat belts in 18 countries resulted in either no change or actually a net increase in road accident deaths.

How can that be? Adams' interpretation of the data rests on the notion of risk compensation, the idea that individuals tend to adjust their behavior in response to what they perceive as changes in the level of risk.

Drivers who feel safe because of seat belts may actually increase the risk that they pose to other drivers, bicyclists, pedestrians and their own passengers. And risk compensation is hardly confined to the act of driving a car. Think of a trapeze artist, or a rock climber, motorcyclist or college kid on a hot date. Add some safety equipment to the equation — a net, rope, helmet or a condom respectively — and the person may try maneuvers that he or she would otherwise consider foolish."

Bottom line: You might actually be MORE safe when driving if you: a) don't buckle up (you'll drive more safely without the protection of a seat belt), or b) install a sharp spike that would come out of the steering wheel on impact (you'll drive a LOT more safely).