In most lists of numbers, the leading digit 1 occurs about 30 percent of the time.

That’s Benford’s Law, named for the American physicist Frank Benford. It’s surprising, but it’s true, and it applies to most statistics relating to society and the natural world, from street addresses to the lengths of rivers.

It can even be used to detect fraud. When people make up lists of numbers, they tend to use too few leading 1s.