Fifty percent of Americans consider themselves environmentalists, according to a recent Gallup poll, but how many put their money where their mouths are? In a survey by Roper, only 29 percent of respondents reported recently purchasing a product because it was advertised as environmentally friendly. Despite efforts to standardize labeling practices, market analysts say consumers are wary of greenwashing. Perhaps more important, they are keeping on an eye on their pocketbooks. With green products like compact fluorescent light bulbs sometimes more expensive at the time of purchase but a better buy in the long run, advocates of responsible consumption say the trick is to reorient consumers so that they begin to think about the lifecycle costs of their every purchase.