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. Imagine, explains Adams, a driver negotiating a curve in the road. Let's make him a young male. He is going to be influenced by his perceptions of both the risks and rewards of driving a car. The considerations could include getting to work or meeting a friend for dinner on time, impressing a companion with his driving skills, bolstering his image of himself as an accomplished driver. They could also include his concern for his own safety and desire to live to a ripe old age, his feelings of responsibility for a toddler with him in a car seat, the cost of banging up his shiny new car or losing his license. Nor will these possible concerns exist in a vacuum. He will be taking into account the weather and the condition of the road, the amount of traffic and the capabilities of the car he is driving. But crucially, says Adams, this driver will also be adjusting his behavior in response to what he perceives are changes in risks. If he is wearing a seat belt and his car has front and side air bags and anti-skid brakes to boot, he may in turn drive a bit more daringly.
The point, stresses Adams, is that drivers who feel safe may actually increase the risk that they pose to other drivers, bicyclists, pedestrians and their own passengers (while an average of 80% of drivers buckle up, only 68% of their rear-seat passengers do). And risk compensation is hardly confined to the act of driving a car. Think of a trapeze artist, suggests Adams, 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. In the case of seat belts, instead of a simple, straightforward reduction in deaths, the end result is actually a more complicated redistribution of risk and fatalities. For the sake of argument, offers Adams, imagine how it might affect the behavior of drivers if a sharp stake were mounted in the middle of the steering wheel? Or if the bumper were packed with explosives. Perverse, yes, but it certainly provides a vivid example of how a perception of risk could modify behavior.
In everyday life, risk is a moving target, not a set number as statistics might suggest. In addition to external factors, each individual has his or her own internal comfort level with risk-taking. Some are daring while others are cautious by nature. And still others are fatalists who may believe that a higher power devises mortality schedules that fix a predetermined time when our number is up. Consequently, any single measurement assigned to the risk of driving a car is bound to be only the roughest sort of benchmark. Adams cites as an example the statistical fact that a young man is 100 times more likely to be involved in a severe crash than is a middle-aged woman. Similarly, someone driving at 3:00 a.m. Sunday is more than 100 times more likely to die than someone driving at 10:00 a.m. Sunday. Someone with a personality disorder is 10 times more likely to die. And let's say he's also drunk. Tally up all these factors and consider them independently, says Adams, and you could arrive at a statistical prediction that a disturbed, drunken young man driving in the middle of the night is 2.7 million times more likely to be involved in a serious accident than would a sober, middle-aged woman driving to church seven hours later.
The bottom line is that risk doesn't exist in a vacuum and that there are a host of factors that come into play, including the rewards of risk, whether they are financial, physical or emotional. It is this very human context in which risk exists that is key, says Adams, who titled one of his recent blogs: "What kills you matters not numbers." Our reactions to risk very much depend on the degree to which it is voluntary (scuba diving), unavoidable (public transit) or imposed (air quality), the degree to which we feel we are in control (driving) or at the mercy of others (plane travel), and the degree to which the source of possible danger is benign (doctor's orders), indifferent (nature) or malign (murder and terrorism). We make dozens of risk calculations daily, but you can book odds that most of them are so automaticor visceralthat we barely notice them.