Governments are beginning to mandate that firms disclose information about social and environmental impacts in their supply chains (e.g., regarding conflictminerals and greenhouse gas emissions). This paper shows that such a mandate will deter firms from measuring (and thus improving) those impacts, for two reasons. First, as demonstrated by our consumer choice experiments, voluntary disclosure of impacts can boost a firm'smarket share. Mandating disclosure reduces a firm's expected gain in market share from learning and disclosing impacts. Second, investors' valuation of a firmdrops upon disclosure that impacts are high. Therefore, to the extent that a manager is concerned about that valuation, a mandate for disclosure will cause her not to learn about impacts, lest she learn and be forced to disclose that they are high
