Scale (gross domestic product), composition (goods and services), and technology (impacts per unit of goods and services) in combination are the proximate determinants in an economy of the resources used, wastes generated, and land transformed. In this article, we examine relationships among these determinants to understand better the contribution that changes in each have made in the past, and might in the future, to reduce the burden placed on the environment by the economy. Using the IPAT equation we assess quantitatively historical changes in scale, composition, and technology in Canada and their respective contributions to changes in environmental impact. The Kaya equation provides a similar framework for a more in-depth consideration of the changes in scale, composition, and technology required to achieve a substantial reduction in global emissions of carbon dioxide. We conclude that it is essential to address scale as part of the solution. (Contains 2 tables and 5 figures.)