Does the positive correlation between infrastructure and productivity reflect causation? If so, in which direction? The author finds that, when growth in roads (the largest component of infrastructure) changes, productivity growth changes disproportionately in U.S. industries with more vehicles....

Yes. We construct a measure of aggregate technology change, controlling for aggregation effects, varying utilization of capital and labor, nonconstant returns, and imperfect competition. On impact, when technology improves, input use and nonresidential investment fall sharply. Output changes...

Modern growth theory suggests that more than three-quarters of growth since 1950 reflects rising educational attainment and research intensity. As these transition dynamics fade, US economic growth is likely to slow at some point. However, the rise of China, India, and other emerging economies...