It works like this: Say two attacks happen in the same general area. Take the time interval between those two incidents, plug it into the equation and it gives an estimate of how many days until the next attack.

“That immediately gives you a time interval between the first two attacks,” explain Johnson, “You take that, put it into the equation and it gives you an estimate.”

It’s only an estimate, Johnson admits, but it’s better than not knowing anything at all.