If you need some small-talk fodder for your next cocktail party, try this: Ever wonder how a vacuum cleaner works? An electric motor drives a wheel of angled fan blades that push a current of air out the exhaust port. The drop in atmospheric pressure behind the airstream creates suction, which pulls everything in front of the vacuum cleaner’s intake port into the machine. On its way through, the air passes through a filter, which traps the dirt in the dust bag—which you dump into the trash. The end.

That basic physics lesson is actually far more significant than party chatter. It’s also been the bane of vacuum cleaner advertisers for 100 years. The basic design of the electric vacuum worked so well that engineers have barely had to alter it. And if nothing important changes about a product, marketers have nothing new to market.

This bit of R&D arcanum helps explain why the 1962 and 2011 ads shown here could almost—just almost—be the same one. “Not that much has changed about vacuums. We’re talking about trapping dust!” says Eric Zeitoun, U.S. president of global brand consultancy Dragon Rouge. “So the only way marketers can distinguish them is with personality.” He’s not joking. What’s really on view in these two ads is not a radical shift in advertising approaches; it’s a look at how the same approach (with a few subtle refinements) still works.

For example, both ads show the vacuum large on the page and framed so it’s coming right at you. “It gives the indication of power,” Zeitoun says. Indeed, both of these machines look ready for a fight. Notice, too, how the viewer perspective is from down on the carpet. “That communicates that the machine can trap dust because you’re at the dust level, physically,” Zeitoun says.

Meanwhile, the “personality” elements are just enough to add some brand panache without disturbing the proven ad template. For instance, “the personality of the GE involves seeing how the housewife lives with and uses the vacuum,” says Zeitoun. Put another way, the vacuum is her friend. Its “versatility” saves her time during a tedious day of chores. (Check out that nifty detachable hose! Look at her smile!)

The Miele’s personality, meanwhile, is more status symbol than friend. The sporty red paint job, the honeycomb exhaust port—this isn’t just an appliance. “It looks like a sports car,” Zeitoun says.

Granted, the consumers who gave these ads but a passing glance may never have noticed these fine touches of personality and character. They saw what vacuum advertisers have always shown them: a nice big photo of a powerful-looking vacuum clawing its way in their direction. No need to knock it. That formulaic view helps suck 1.1 billion consumer dollars into the vacuum cleaner business every year.