Once upon a time Americans knew exactly where they wanted to go to buy a new car—to the same dealer that sold them their last automobile. But the storied days of brand loyalty have disappeared, thanks to the implosion of the Big Three in Detroit and growing discrimination among consumers that has even weakened the branding power of foreign manufacturers like Toyota.
Two decades ago four out of five Americans were repeat buyers of the same car brand, continuing a long tradition of “Ford families” or “Chevy families....