This week marks the semi-official start of the holiday shopping season, but chances are the catalogs have already been piling up at your house. That’s right, paper catalogs are still big business in the digital age.

The reason is pretty simple, really: “Catalogs work,” says Hamilton Davis, president of the American Catalog Mailers Association. He says about two-thirds of catalog orders are placed online, but lots of people still make their choices by flipping through glossy pages.

“The internet’s a great shopping vehicle if you know what you’re looking for, but it’s not a great browsing vehicle,” he says.

Lest you think you’re more popular with Pottery Barn and Brookstone than you used to be, catalog mailings are down — to 12.5 billion last year from 20 billion in 2006, according to industry groups.

It’s not just because of the Web. “The catalog business really started to get hit before the digital age by the increasing postal rates,” says retail analyst Stephen Platt.

Five years ago, catalog rates jumped almost 23 percent. The post office, which just reported a record annual loss, is under pressure to raise rates again next year.