PHOTO RENDERINGS BY PATRICK WHITE 11OPENING ARGUMENTremains 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 wed-
dings, and engaging in a host
of other energy-intensive activ-
ities 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 pro-
vides 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 cir-
cles, 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,
square feet today. Without
invoking the power of behav-
ioral contagion, it’s difficult to
explain this change.
But here is the cause for
hope: Where contagion cre-
ates 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.
Solar-panel adoption, for
example, is particularly con-
tagious. After controlling for
a variety of other potentially
important causal factors, one
study found contagion’s power
in this domain to be substan-
tial: Each new installation
in a neighborhood can, over
time, lead to several additional
ones. (In a follow-up study,
researchers have found evidence
that solar panels visible from
the street exert a significantly
greater peer effect than those
that aren’t—further suggestingthat our neighbors’ behavior
affects our own.) The conta-
gion effect in solar adoption
can be seen in Google’s Project
Sunroof, which displays aerialphotos of neighborhoods and
identifies houses with solar pan-
els by placing red dots on their
roofs. Those houses tend to be
near others with red dots.