Although eco-efficiency is a rather new method, the idea is not. In the early 1970s Paul R. Ehrlich and John Holdren developed the lettering formula I = PAT to describe the impact of human activity on the environment.[4] Furthermore, the concept of eco-efficiency was first described by McIntyre and Thornton in 1978,[5] but it wasn't until 1992, when the term was formally coined and widely publicized by Stephan Schmidheiny in Changing Course.[4] Schmidheiny set out "to change the perception of industry as being part of the problem of environmental degradation to the reality of its becoming part—a key part—of the solution for sustainability and global development."[6] The major drivers in the early phase of eco-efficiency's development were the "forward-looking managers and thinkers in 3M and Dow."[6] It was their involvement which catapulted eco-efficiency from a brilliant idea to a workable concept. The results of the WBCSD's work creating the "linkage between environmental performance and the bottom line was published in 1997 in its report Environmental Performance and Shareholder Value."[6]