This research explores the effect of source certainty-that is, the level of certainty expressed by a message source-on persuasion. The authors propose an incongruity hypothesis, suggesting that source certainty effects depend on perceived source expertise. In three experiments, consumers receive...

We study the impact of mandatory calorie posting on consumers' purchase decisions using detailed data from Starbucks. We find that average calories per transaction fall by 6 percent. The effect is almost entirely related to changes in consumers' food choices—there is almost no change in...