Social responsibility: U.S. power plants 1985–1998

This study introduces an Environmental Performance Index (EPI) to assess the performance of firms that produce both good and bad outputs. In the one good output one bad output case, the EPI simplifies to the ratio of good–bad output for period t + 1 and period t. After deriving the index, data for U.S. coal-fired power plants from 1985 to 1998 are used to demonstrate insights that the EPI can provide. We find that power plants with units participating in Phase I of the Acid Rain Program experience a dramatic improvement in their EPI during 1994–1995.