Dear Economist,

When I travel I am faced with a difficult choice: which of the toilet booths to use in offices or hotels. I always try to guess which one is the least used. Probability theory should tell me that all the booths should be equally used, but perhaps human psychology plays a part in this. My boyfriend believes the last one is the least used – contrarily, I believe the opposite. Perhaps this proves that, on average, all are equally used. Which one do you use?

Jan Lucan, Prague

Dear Jan,

The efficient market hypothesis says that stock and bond traders will swoop on underpriced assets, driving their prices up. If so, an ignorant investor may pick and choose at random, knowing that her selections will be priced as keenly as any others.

Let us assume that everyone, like you, wishes to use the stall less travelled. Can we apply the hypothesis to public lavatories? If so, you may pick any stall you wish.

But the efficient market hypothesis is not universally accepted even in financial markets, and in public toilets it is less convincing. After all, there are no highly paid “toilet traders” engaging in arbitrage – or if there are, the term conventionally applies to a different profession altogether. So perhaps there are systematic errors to exploit.

Internet research uncovers one poll that suggests that many people, like your boyfriend, head to the farthest cubicle. Another site claims that the nearest stall is the least used.

But all this is a little puzzling. Your stall-picking strategy reminds me of Warren Buffett’s comment that “diversification is a protection against ignorance”. Presumably you just want a clean toilet with some paper. Would it kill you to do a little research and check a couple of stalls? That’s what I do.

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