Social scientists have demonstrated the influence of peer behavior in a host of other areas. One study, for example, found that when military families were posted to a new location where the obesity rate was 1 percent higher than average, adults in the families were 5 percent more likely to become obese during the course of their assignment there. Behavioral contagion—as the phenomenon is known—can exacerbate bullying, cheating on taxes, and problem drinking, among other harmful behaviors. But people also become more likely to exercise and eat prudently when those behaviors become more widespread among peers.
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Given the power of contagion, it is astonishing that the question of how policy makers might harness this power has received so little serious attention. Even when smoking restrictions were enacted, for instance, it was primarily to protect nonsmokers from secondhand smoke. But the damage done by secondhand smoke pales in comparison with the harm caused by becoming a smoker—not just to the smoker himself, but also to his peers, who in turn become more likely to smoke.
The behaviors that spawned the climate crisis are perhaps even more contagious than smoking, a fact that has gone largely unnoticed by economists and climatologists, who understand global warming as a consequence of greenhouse gases being costly to eliminate and dischargeable without penalty. This assessment leads naturally to pessimism, since the costs of carbon removal remain high and political opposition to robust taxation remains formidable. It also overlooks contagion’s potential power to help address this crisis.
We’ve been building bigger houses, driving heavier vehicles, commuting longer distances, staging more destination weddings, and engaging in a host of other energy-intensive activities only partly because their true costs to the planet are not fully priced in. The far more important reason we’ve done these things is our tendency to behave as our peers do.
The housing market provides a vivid illustration of this. Since the early 1970s, the lion’s share of national income growth has accrued to the wealthy, who used some of their gains to build ever larger houses. The near-wealthy, who travel in the same social circles, also built bigger, and so on down the income ladder. Although median incomes grew little during the past half century, the median new house grew from about 1,500 square feet in 1973 to almost 2,400 square feet today. Without invoking the power of behavioral contagion, it’s difficult to explain this change.
But here is the cause for hope: Where contagion creates a problem, it can also help solve it. Just as in the case of smoking, where peer effects exacerbated and then reduced the prevalence of the practice, so too could contagion help us meet the climate challenge.