Remember at the beginning of summer when Homeland Security chief Michael Chertoff ramped the nation up a notch on alert for terrorist attacks based on what he called his “gut feeling?” Well, an economist has actually looked at something called data and determined that it must have been something Chertoff ate because his indigestion sure wasn’t based on hard evidence of a clear and present danger.

Alan Krueger, a professor of economics and public affairs at Princeton who served as the chief economist at the Labor Department from 1994 to 1995, says government officials should avoid making vague statements about terrorism that have little empirical basis. Krueger decided to test Chertoff’s “gut feeling” about seasonal patterns of terrorist activity against data on worldwide terrorist attacks from the National Counterterrorism Center, the federal agency responsible for compiling terrorism statistics. His conclusion might leave you a little queasy: “I wouldn’t draw too strong a gut feeling from this data.”

The economist found that, historically, attacks by al Qaeda and Sunni extremist groups have been no more frequent in the summer months. When all terrorist groups are counted, the number of attacks worldwide has been about 10 percent higher in July and August than in other months, he said. But he characterized this as a small difference, noting that other types of incidents such as boating accidents go up by much more than 10 percent in the summer.

“Would you scare 300 million people on the basis of those tiny blips in those charts?” Krueger asked. “It didn’t seem to me to be constructive.”

But this is the never-ending war on terror, which has nothing to do with “constructive.” Chertoff’s belly bubblings follow a familiar pattern established since 2001 — periodically, citing ever-so-vague reasons, government officials bump us up a color or two on their handy apprehension scale.

Perhaps, since we’re using Chertoff’s guts to predict terrorism like we used Grandma’s elbow to predict rain, we should revert to having soothsayers read the future in intestines — say Chertoff’s or any other official’s who gets his jollies cranking up the national anxiety meter. I bet then we’d see a less somatic, more scientific approach to assessing the terror threat.