While more and more Americans are shopping online in lieu of going to stores, this trend has not yet hit the retail grocery industry in a significant way. Nine percent of U.S. adults report their household orders groceries online for pickup or delivery at least once a month, including 4% who do it at least weekly. By contrast, almost all Americans say someone in their family shops for groceries in person at least once a month, with 83% going at least once a week. This pattern -- highly frequent grocery shopping occurring mostly in person -- highlights the theoretically enormous potential for growth in the online grocery business. Amazon's purchase of the retail grocer Whole Foods recently underscored this possibility, giving rise to speculation the online giant will use the grocery chain as a launching pad to expand its online operations into the food sector.