Findings of inverted-U relationships between income and certain types of pollution have generated considerable controversy, yet relatively little is known about the factors underlying these relationships. U.S. emissions of several major air pollutants have begun to decline, mirroring the...

Findings of inverted-U relationships between income and certain pollutants have generated considerable controversy, yet relatively little is known about the factors underlying these relationships. U. S. emissions of several major air pollutants have begun to decline, mirroring trajectories found...