Insurgents’ homemade bombs, known as improvised explosive devices, look increasingly like a lasting fixture on the early-21st century battlefield. The Pentagon’s bomb squad warns that the cheap, easily fabricated family of explosives are spreading all around the world. But it doesn’t know how long the devices themselves last.

The Joint Improvised Explosive Device Defeat Organization, JIEDDO, collects sheafs of data about the bombs. It knows what sorts of materials go into the bombs, where the materials come from, what countermeasures succeed at stopping the blasts (and which ones fail), and how many of them turn out to be duds. But to date, it hasn’t acquired any data about the lifespan of an improvised explosive device.