After 350,000 Coin Tosses, Scientists Prove Football's Toss Is Unfair

Researchers at the University of Amsterdam set out to settle once and for all whether a coin toss is truly a fair method of drawing lots. After tossing a coin 350,000 times and meticulously recording every result, they found the odds are not exactly fifty-fifty.

When you place a coin heads-up on your thumb and flip it, it lands heads 51% of the time. Start with tails, and it lands tails 51 out of 100 times on average. After days-long coin-tossing marathons, it can now be stated with certainty: the toss used in many sports is not fair.

This fascinating result was predicted years ago by Stanford statistician Persi Diaconis. He described how a tossed coin is influenced by more than just vertical force and rotation speed - the coin also wobbles mid-air.

"A good magician knows this," says Professor Eric Jan Wagenmakers. "A magician can flip a coin and catch it with the same side up every time. The trick is that the coin doesn't actually flip - it just wobbles like a pizza tossed in the air, but you can't see it because it happens too fast."

Even with a fair throw, the coin lands in the same orientation it started slightly more often. "The difference is tiny. Diaconis was delighted when we sent him our results - he predicted exactly 51% based on theory. Though he's the kind of scientist who would have found it just as fascinating if we'd gotten a different percentage."

Wagenmakers hopes the study qualifies for an Ig Nobel Prize, the alternative Nobel awarded to amusing research that makes you think. The researchers worked on this study entirely in their spare time, without any funding. "Otherwise the reaction would surely have been: is this what scientists do with my tax money?"