Calorie postings, self control, and the holidays

Today's Times covers a paper on caloric consumption after a new signage law. Researchers at Stanford obtained high-frequency transactions data from Starbucks around the imposition of the NYC law requiring calories be posted at large chain restaurants. The data revealed that NYC customers reduced their caloric intake when they knew how much they were consuming. Except during the holidays, when presumably good cheer or something else overcame the effects of new knowledge!