In Cambridge, the average height of pedestrians has risen by an inch--not because of a growth hormone dreamed up in an MIT laboratory, but because of a new trend in footwear.

Choose someone dressed in neo-hippie Clothing--cut-offs, flannels and beads. Inspect the person's feet, and you'll find out why people seem taller these days.

The pedestrian is probably wearing sandals. They might be clunky, inch-thick corksoled ones with fat leather straps. Or, they could be inch-thick black rubber-soled contraptions, secured to the person's feet by brightly colored nylon straps.

These intrinsically unattractive shoes, designed mainly for comfort, have become the latest trend in footwear. Cork-soled Birkenstocks and rubber-soled Tevas are spotted on Harvard Square feet with increasing frequency.

National sales of both styles of sandals have increased dramatically, manufactures say.

"Sales are just phenomenal," says Lisa Geil of Birkenstock, based in Novato, California. And Geil says sales are especially strong in college towns.

Similarly, Deckers Corporation, which makes and markets Tevas, "has doubled in size for at least the last three years," says spokesperson Ken C. Fish.

The company is expecting to make $30 million in shoe sales this year. Last year Deckers made $11 million.

The customers who help the companies rack up these astounding sales figures all deny that they've bought into a fad. They don't deny the fad's existence; they simply blame the fed on other people.

"A lot of rich preppie kids wear them. They're pseudo-deadheads," says Sarah K. Luecke, a rising sophomore at Brooks School.

And still, there is the pesky race to be on the cutting edge of fashion, "I got my Birkenstocks before they were trendy and cool," a Harvard Square regular asserts.

Most wearers recently accosted in the Square cite comfort as the main reason for wearing the trendy sandals. The old credo of the fashion-conscious, "It's better to look good than to feel good," appears to falling by the wayside.

"I wear [Birkenstocks] not because I'm a hippie burnout, but because they're the most comfortable shoes you can buy," says Marc C. Foster, a rising senior at Lexington High School, though he admits that his choice of footwear may be directed by his parents' "clog genes hanging on."

"I like the style, the look, and the comfort," Lucy Karaszewski of Manassas, Virginia says of her Birkenstocks and those of her two children.

Standish Bradford, 15, expresses similar sentiments about his Tevas. "They're comfortable. When it's sunny you don't have to deal with shoes."