Recently, there has been a proliferation of measures responding to demands for accountability and transparency. Using the example of media rankings of law schools, this article argues that the methodological concept of reactivity - the idea that people change their behavior in reaction to being evaluated, observed, or measured- offers a useful lens for disclosing how these measures effect change. A framework is proposed for investigating the consequences, both intended and unintended, of public measures. The article first identifies two mechanisms, self-fulfilling prophecy and commensuration, that induce reactivity and then distinguishes patterns of effects produced by reactivity. This approach demonstrates how these increasingly fateful public measures change expectations and permeate institutions, suggesting why it is important for scholars to investigate the impact of these measures more systematically.