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Externalities of Testing: Lessons from the Blizzard of 2010

A good place to contemplate the virtues of rational human behavior was at the corner of Connecticut and Nebraska avenues, in Washington, DC, 5 days after the region was slapped with the worst blizzard of the past 100 years. Main roads were by then reasonably clear; traffic was returning to an almost normal (i.e., congested) flow, and many sidewalks were passable thanks to the spade work of homeowners who wanted to go outside without skis or who hoped their neighbors would drop by with bowls of hot soup. But at the corner of Connecticut and Nebraska, a notoriously busy and dangerous intersection even in the dry seasons, there was no way for pedestrians to cross the street. Mountains of snow created by the plows, coupled with the absence of a clear incentive for individuals to shovel through them, made the corner essentially impassable. The resulting mess, replicated at just about every such corner intersection in the city, required people to take great risks to climb 3 and 4 foot icy dunes and then slide down into the path of moving cars, or to trudge extra yards in biting wind in search of a narrow clearing. It was all a painful reminder that seemingly rational individual behavior can sometimes lead to calamitous social outcomes, and confirmed again why the theory of “externalities” has such a hallowed place in social science. The decision calculus is irritatingly logical. Plow truck drivers have a single goal, to clear main streets for vehicular traffic, which compels them to push as much of the snow to the curb