Solving the mystery of the elusive "short" cappuccino.
The modern equivalent is the airport departure lounge. Airports could create nicer spaces, but that would frustrate the ability of airlines to charge substantial premiums for club-class departure lounges.
Starbucks' gambit is much simpler and more audacious: Offer the cheaper product but make sure that it is available only to those customers who face the uncertainty and embarrassment of having to request it specifically. Fortunately, the tactic is easily circumvented: If you'd like a better coffee for less, just ask.
Tim Harford is a Financial Times columnist. His latest book, The Logic of Life, will be published in paperback on Feb. 10.
Illustration by Mark Alan Stamaty.