Why is milk stored in rectangular cartons, and soft drinks in round cans? (Ruth Fremson/The New York Times)

Robert H. Frank's economic guidebook unlocks everyday design enigmas

Published: July 8, 2007

LONDON: Have you ever wondered why some cars have fuel fillers on the left, and others on the right? Why your VCR is stuffed with functions that you'll never use? Why women button their clothes from the left, and men from the right? Or why CD cases are smaller than DVD cases when the discs are the same size?

We encounter puzzles like these every day. They're not life-threatening or planet-imperiling, but they don't make sense, not at first, anyway. The American economist, Robert H. Frank, has devoted a book, "The Economic Naturalist," to unraveling them. His explanations for what he calls "everyday enigmas" are rooted in economic theory, but many of them also illuminate anomalies in the design of the things that fill our lives.

The issues explored in the book were suggested by the students on the introductory economics course Frank teaches at Cornell University. He asked them to find economic explanations for things that flummoxed them in daily life. Frank, who has flirted with design before, notably in his self-explanatorily entitled book, "Luxury Fever: Why money fails to satisfy in an era of success," then devised his own answers to the most interesting questions. His objective was to show that, beneath the jargon and mathematical formalism, economics is grounded in common sense.

Some of the questions and answers in "The Economic Naturalist" are purely economic. Why are brown eggs more expensive than white ones? Because the hens that lay them are bigger and tend to eat more. Why is it so hard to find taxis in the rain? Because many drivers stop work after hitting their daily fare targets, which they do faster in wet weather when more people use cabs. The grist of Frank's argument is that most business decisions are determined by the cost-benefit principle, whereby you only do something if the benefit gained is greater than the cost incurred. And the application of this principle exerts considerable influence on design.

A simple example is the over-complicated VCR. Why do manufacturers load them up with so many functions - most of which we seldom, if ever, use - that recording a television program is infuriatingly difficult? The answer is because it costs so little to add each function to a VCR that is cheaper to install them on every machine - just in case anyone wants them - than to "edit" models for different customers. Frank could have made an identical case against the over-complicated cellphone.

The same argument explains why Braille keypads are fitted on drive-by cash machines, even though the people who use them are unlikely to be able to see clearly enough to drive. Again the cost-benefit principle means that manufacturers can't justify the additional cost of producing one set of machines with Braille keypads, and another set without them.

Other anomalies are historic. Take the positioning of buttons on clothes. Why are they on the right for men, and the left for women, especially since, for the 90 percent of the population who are right-handed, it's much easier to do up buttons from the right? It's because when buttons were introduced in the 17th century, they were affordable only by the wealthy. As rich men then dressed themselves, they did so from the right; whereas wealthy women were dressed by servants, who preferred to button them up from the left. The custom continues today, even though fewer women are dressed by servants, because there has been no incentive for the fashion industry to change it.

Or think of the seemingly illogical difference in size between the packaging of (identically sized) CDs and DVDs. This dates back to the 1980s, when retailers were replacing 12-inch, or 302-millimeter, vinyl LPs with CDs, and realized that there would be enough space in each old LP rack for two rows of CDs, if the cases were just under 5 inches high. Yet when DVDs came out in the 1990s, they were displayed alongside videocassettes, whose cases were more than 7 inches high, so DVD packaging was made to the same height.

The explanations for other everyday enigmas are vested in the present. Why, for instance, is milk stored in rectangular cartons, and soft drinks in round cans? It's because it's easier to hold a round can when downing a cola, whereas comfort isn't as important to us when we're pouring milk from a carton, as we don't hold them for as long. That's why manufacturers use rectangular milk cartons, which can be packed more efficiently as they occupy less space in pallets, trucks and shop shelves. There's also a financial incentive. Milk is stored in refrigerated cabinets, so the space it occupies is more expensive to operate than the open shelves occupied by soft drinks.

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