COMPUTER MODELS HAVE THEIR LIMITS: Models’ Projections for Flu Miss Mark by Wide Margin.

In the waning days of April, as federal officials were declaring a public health emergency and the world seemed gripped by swine flu panic, two rival supercomputer teams made projections about the epidemic that were surprisingly similar — and surprisingly reassuring. By the end of May, they said, there would be only 2,000 to 2,500 cases in the United States.

May’s over. They were a bit off. On May 15, the Centers for Disease Control and Prevention estimated that there were “upwards of 100,000” cases in the country, even though only 7,415 had been confirmed at that point. . . . What went wrong?

The leaders of both the Northwestern University and Indiana University teams seemed a bit abashed when they were asked that last week.

This is why it’s a bad idea to make policy based on computer models, unless they’ve been proved out by extensive experience.