Some consumers can pressure a company into changing its habits, but they're not the folks in the checkout lines.
The most influential consumers are institutions, local governments, and other companies.
"These kinds of policies that come up politically - even in city councils - end up being a headache for companies to deal with," says Karen Paul, professor of business environment at Florida International University in Miami.
For example, South African companies paid scant attention when individual Americans boycotted their products. But when cities joined the protest, the companies felt the pinch.
That doesn't mean consumers should give up on value shopping, says Steven Lydenberg of KLD, a social investment research firm in Cambridge, Mass.. "I would do it irrespective of whether the company heard.... It does make a difference - to me."
But to really be heard, people should write to the company, and explain why they are or are not buying the product, he says.
For example, if a company's environment officer can show that consumers pay attention to the company's recycling stand, she's more likely to get support for stepping up the program.
"I can't quantify that a company literally changed its testing policies as a result of consumer pressure," says Clare Haggarty, a spokeswoman for the National Anti-Vivisection Society, but companies have reduced their product testing on animals since consumers objected to methods they considered cruel.
"It's our belief that within the next decade, almost all cosmetics and personal-care products won't be tested on animals," she adds. "I firmly believe that it will come about because of consumer pressure."