Philip W Schiller, Apple’s vice president for marketing, strode across the stage of the California Theater in San Jose last week trumpeting the virtues of new Apple products. As he caressed the side of the latest iMac personal computer, he noted how thin it was – 5 millimeters, 80 percent thinner than the last one. Then he said, with an air of surprise, as if he had just thought of it: “Isn’t itamazing how something new makes the previous thing instantly look old?”

Umm, yes, Mr Schiller, you design your products that way. It is part of a strategy that Apple has perfected. How else can the company persuade people to replace their perfectly fine iPhone, iPad, iMac and iEverything else year after year?

In the past, electronics makers could convince consumers that the design was different, because it actually was. The first iMac, for example, was a blue bubble. Then it looked like a desk lamp, and now it is a rectangular sheet of glass with the electronics hidden behind it. The iPod designs changed, too, over time, before they became progressively smaller sheets of glass.

Certainly makers add features like better cameras or tweak the software – Siri and Passbook on theiPhone are examples of that for Apple – to persuade people to upgrade. But in the last few years, consumer electronics have started to share one characteristic, no matter who makes them: They are all rectangles. Now, companies like Apple, Amazon, Microsoft and Google need to persuade consumers to buy new rectangles once a year.

“This phenomenon happened to the TV manufacturers a few years ago. They all started to look the same: flat panels on a wall,” said Donald A Norman, author of “The Design of Everyday Things.”

The consequences for manufacturers were disastrous. “Customers no longer had to buy the higher-end Sony model; instead, they could get the cheaper, Chinese one,” Norman said. “This is what today’s companies are scared of. Turn off the screen on a smartphone or tablet and they look identical. They’re just rectangles.”

Each year, Apple and other companies seem to put those rectangles in a vise, flatten them slightly, alter the exterior dimensions and showcase them as the next big, or little, thing. (Apple did not comment on its design strategy.)

This was not always the case. As a child I remember exploring my father’s Minolta film camera – a camera from the mid-1950s that was given to him by his father. Although film cameras are now for the most part obsolete, you can bet that camera can still take 36 pictures without a hitch.

Yet can you imagine, 10 years from now, someone handing a child an iPad Mini, the latest Apple gadget? They would scoff, just as people do today when they see an older – 2 or 3 years old – version of the iPhone.

There is a term for all of this: “planned obsolescence,” which was popularised in the 1950s by Brooks Stevens, an industrial designer who specialised in making new cars. Briskly adopted by post-war consumer goods industries, the strategy coaxed Americans to sell their 1955 Cadillacs for the 1956 Cadillacs with their pronounced tail fins, and then the 1957s with even more exaggerated fins, and then ’58s, ’59s and so on.

Stevens’ term was often misinterpreted as meaning things were designed to fall apart on a regular schedule. But he believed that true upgrades and design changes would make people want to buy the latest thing. That still holds true in this era, when consumers are supposedly wary of the hucksterism of manufacturers. If you don’t upgrade to the latest iPhone or iPad, you fear you may look dated and clueless, even though the rational part of your brain says, “This is a perfectly fine, useful device.”

Consumer electronics companies, Norman noted, have adopted the same marketing techniques the automobile industry perfected decades ago.

“This is an old-time trick – they’re not inventing anything new,” he said. “Yet it’s to the detriment of the consumer and the environment, but perhaps to the betterment of the stockholder.”

He added: “For Apple, you forgot the other trick: change the plugs!” While the rest of the electronics industry has adopted micro-USB ports, Apple just changed the proprietary ports and plugs on all of its latest devices – laptops, iPads and iPhones included.

Even so, my first iPod still plays music. My laptop from four years ago can still browse the Web. And my first e-readers can still display books.

It seems some consumers are starting to feel upgrade fatigue. There is no lift in PC sales, and people are owning them longer. A report by Recon Analytics, a market research firm, found that people around the globe were waiting longer to buy new mobile phones. In 2007, Americans upgraded their phones every 18.7 months on average; three years later, that number had stretched to 21.1 months. In Finland, people now wait 74.5 months to upgrade, compared with 41.8 months in 2007.

Maybe Schiller’s comment about the iMac isn’t how consumers see it anymore. Instead, people are starting to realise that these upgraded products are simply flatter rectangles that don’t really offer much more than the last model. Just like the tail fins on the ’56 Cadillac.