This paper analyzes the sources of U.S. productivity growth through 2004 and presents medium-term projections for the U.S. economy. We attribute a substantial portion of productivity gains over the past decade to production and use of information technology equipment and software. In the most recent years, we also identify a growing contribution from sources outside the technology- producing sectors. Our base-case projection for the GDP growth rate is almost exactly three percent. We emphasize the substantial range of uncertainty by presenting an optimistic projection of 3.5 percent and a pessimistic projection of only 1.9 percent.