The hidden cost of 9/11
More lives were lost, as Americans chose driving over flying
In the months after the terrorist attacks of September 11, 2001, Americans shunned airports and instead, took to the nation’s highway — presumably on the belief that vehicular travel was a safer option. Yet what seemed a better bet ended up costing more lives, because travelers shifted to a more dangerous mode of transportation, according to research by Johnson professor of marketing and economics Vrinda Kadiyali.
“After controlling for observable and unobservable factors that influence fatalities, we estimate that as many as 2,300 lives were lost, because of travelers’ response to 9/11,” write Kadiyali and her co-authors, Garrick Blalock and Daniel H. Simon of Cornell’s Dyson School of Applied Economics and Management, in “Driving Fatalities After 9/11: A Hidden Cost of Terrorism,” published in Applied Economics, Vol. 41, Issue 14, 2009. “These deaths are a hidden cost of the 9/11 attacks.”
Travelers appear to have avoided flying not only because they thought it was safer but also because they wanted to avoid delays and hassles associated with increased airport security, according to the researchers.
“These extra security measures are imposed to tell people that it is safer to fly,” Kadiyali says. “But, because of those measures, fewer people choose to fly, and when they drive instead of flying, more people die on the road.”
The researchers analyzed data on all motor vehicle fatalities in the U.S. between 1994 and 2003. Highway deaths increased significantly after 9/11, the researchers found. To isolate the so-called “9/11 effect” the researchers used statistical analysis to control for variations in air fares and general economic conditions.
They also compared data on fatalities involving commercial vehicles — primarily trucks transporting cargo — and non-commercial vehicles, such as passenger cars. If a 9/11 effect did exist, there would be higher death rates for non-commercial vehicles, since commercial vehicles would be on the road, regardless of terrorism fears, the researchers hypothesized. In fact, the researchers found that fatalities involving commercial vehicles did not increase after 9/11, while deaths involving non-commercial vehicles spiked.
They also identified several additional signs of a 9/11 effect. Outof- state fatalities increased more than in-state fatalities — evidence that travelers substituted highway for air travel. And fatalities went up most in the Northeast, where typical travel distances are shorter and driving is an attractive alternative to flying.
Also, the increase in auto deaths weakened over time, with fatalities returning to pre-9/11 levels by October 2003. According to the researchers, this probably happened because fear of flying lessened, and travelers adjusted to airport security measures.
But in the two years the 9/11 effect held sway, more than 2,000 people died on the nation’s highways, according to Kadiyali.
“When we did the calculation and found the number, my heart sank,” she says. “Look at how imperfectly we make decisions and what the cost can be, when we improperly assess risk.”