"Minimalist economists stubbornly resist Charles Kindleberger's characterization of investor expectations in a financial bubble as "irrational." This paper seeks to resolve the controversy by imbedding Kindleberger's well-researched, impressionistic theory of financial crises into an expanded, but still-minimalist model of rational expectations. Introducing the concepts of malicious disinformation and rational overpromotion creates an informational environment in which it is time-consuming and costly to distinguish fact from fiction. Rationality still requires that expectations and market fundamentals move together over long periods of time, but dishonorable overpromoters can earn substantial profits in the interim"--National Bureau of Economic Research web site.