Exactly forty years after Eugene Fama’s (1965) article “The Behavior of Stock Market Prices” (Journal of Business), the play ”E?cient Capital Markets” is still going strong. With his thesis, Frank Ecker is adding a new act to the play: His work is a combination of several new developments on the analytical and empirical capital market research front. Capital market e?ciency is based on two aspects. First, the ability of investors to identify a situation in which asset prices are out of the capital market equilibrium. Second, on the possibility of the market to make arbitrage pro?ts by driving the prices back to the equilibrium value. Both aspects are conditional on the set of ”relevant” information. As a result, the basic question is: What is relevant information and how is it processed by investors? This work is building on the concept of information quality, information uncertainty or information risk. Fama’s e?cient market hypothesis is just a special case based on the assumption that new information is absolutely correct and completely credible to all investors. In contrast, this work makes use of the more general assumption that new information can be characterized by very di?erent degrees of credibility, or qu- ity. The setting of initial public o?erings is chosen as one of the few capital market transactions arguably characterized by high information asymmetry between the ?rm’s insiders (management) and outsiders (investors).