http://freakonomics.com/2011/09/08/how-are-sharks-less-dangerous-than-vending-machines-an-exercise-in-conditional-risk/ http://freakonomics.com/2011/09/08/how-a

http://freakonomics.com/2011/09/08/how-are-sharks-less-dangerous-than-vending-machines-an-exercise-in-conditional-risk/ http://freakonomics.com/2011/09/08/how-are-sharks-less-dange... might be good? You could also remind them that ~90 people die every day from car crashes. Each month more people die from car crashes than have died in terrorist attacks on the US. A similar number of people (to the number that die in car crashes) die from gun violence in the US. Terrorism should realistically be so far down on someone's lists of cars that they shouldn't be able to justify any ounce of worry on it. Driving more cautiously would be a better use of the anxiety.