Are labs the most popular breed of dog? I don't know. I do know that I had a Lab/German Sheperd growing up, and she was a great dog. Anyway, here is a link to the article:
Why Americans love Labrador retrievers
Not too long ago, Labrador retrievers were considered a tad exotic. In the 1950s, the sporty mid-size breed was a suburban rarity, popular mainly among upper-crust Anglophiles who liked the idea of owning a dignified hunting dog. Today, however, Labs are the Levi's jeans of purebred dogs. They've topped the American Kennel Club's list of registered canines for 12 years straight. And not just topped, but dominated: The number of registered Labs is nearly three times the number of golden retrievers, the second most popular dog on the list.