<DIV><P>In the past three decades, the number of obese adults in the United States has doubled and the number of obese children almost tripled, which may lead to increased medical expenditures, productivity loss, and stress on the health care system. Economic analysis now shows that weight gain is the...</p></div>

<DIV>Conventional wisdom once held that the demand for addictive substances like cigarettes, alcohol, and drugs was unlike that for any other economic good and, therefore, unresponsive to traditional market forces. Recently, however, researchers from two disparate fields, economics and behavioral...</div>