A few weeks back we discussed the perspective that the economic meltdown could be viewed as a global computer crash. In the NYTimes magazine, Joe Nocera writes in much more depth about one aspect of the over-reliance on computer models in the ongoing unpleasantness: the use of a single number to assess risk. Reader theodp writes: "Relying on Value at Risk (VaR) and other mathematical models to manage risk was a no-brainer for the Wall Street crowd, at least until it became obvious that the risks taken by the largest banks and investment firms were so excessive and foolhardy that they threatened to bring down the financial system itself. Nocera explores the age-old debate between those who assert that the best decisions are based on quantification and numbers, and those who base their decisions on more subjective degrees of belief about the uncertain future. Reliance on models created a 'false sense of security among senior managers and watchdogs,' argues Nassim Nicholas Taleb, who likens VaR to 'an air bag that works all the time, except when you have a car accident.'"