Financial firms engage in a wide range of private conduct. New rules that address financial risk can regulate elements of that conduct but not all conduct or all the factors that affect conduct. There is, therefore, a real concern that new regulation will have unanticipated consequences, particularly in a system as complex as the financial markets. The result may be new risks or a shift in risk taking away from regulated conduct — responses that regulators can anticipate but may not be able to accurately predict or control. This Article cautions against the rush to adopt new financial risk regulation without first assessing its broader impact on risk taking. Attempting to do so with limited information may be difficult. For illustration, it...