This study assesses the effectiveness of two types information disclosure programs - state-based mandatory carbon reporting programs and the voluntary Carbon Disclosure Project, which uses investor pressure to push firms to disclose carbon emissions and carbon management strategies. I match firms in each program to control groups of firms that have not participated in each program. Using panel data methods and a difference in differences specification, I measure the impact of each program on plant-level carbon emissions, plant-level carbon intensity, and plant level output. I find that neither program has generated an impact on plant-level carbon emissions, emissions intensity, or output. Placing this study in contrast with others that demonstrate improvements from mandatory information disclosure, these results suggest that how information is reported to stakeholders has important implications for program effectiveness. (C) 2012 Elsevier Ltd. All rights reserved.