The impulse to go “green” is spreading faster than morning glories. Organizations of all types are launching green campaigns—from London’s congestion charge on automobiles to Wal-Mart Stores’ push to sell organic foods. In almost every opinion poll on the subject, consumers say they are very concerned about climate change, and they connect the dots back to their own purchases, according to a 2007 McKinsey survey of 7,751 people in Brazil, Canada, China, France, Germany, India, the United Kingdom, and the United States. Indeed, the poll shows that 87 percent of consumers worry about the environmental and social impact of the products they buy.

But when it comes to actually buying green goods, words and deeds often part ways. No more than 33 percent of the consumers in our survey say they are ready to buy green products or have already done so. In a 2007 Chain Store Age survey of 822 US consumers, only 25 percent of them report having bought any green product other than organic foods or energy-efficient lighting. Indeed, most of the green goods on the market have tiny market shares. In 2006, green laundry detergents and household cleaners accounted for less than 2 percent of US...