When the first Earth Day took place in 1970, environmentalists believed that the key to solving many of the pressing problems with air and water pollution was to limit economic activity and the living standards of people everywhere. They even had a formula for this taught in colleges, I=PAT, or environmental impact equals population times affluence times technology. But columnist John Tierney of the New York Times notes that many of these early notions were misplaced, as experience soon revealed that wealth actually fuels investment in environmental protection. Thus, maybe to the surprise of these Earth Day activists, a healthy environment is best preserved through fostering a prosperous, thriving economy.