The Hidden Spare Key: How Much of a Burglar's Search the Common Hiding Places Already Cover

A spare key hidden outside the house is a second front door whose lock is the obscurity of its hiding place, and obscurity can be priced. This study uses a stated distribution of hiding places among households that hide a key, from 22 percent under a mat down to single-figure novelties, and models an intruder who searches places in order of popularity at 40 seconds per place. The three commonest places, mat, fake rock and plant pot, already cover 49 percent of hidden keys; the first five places cover 66 percent and take 3.33 minutes to search; eight places cover 83 percent in 5.33 minutes. Only the tenth category, genuinely original places at 10 percent, lies outside a short search. The conclusion is that a hidden key in any commonly used place should be treated as a key handed to a patient stranger, and the safe alternatives are a coded key safe, which replaces obscurity with a combination, or a key left with a person rather than an object. SIMULATED, NOT MEASURED.