The past decade has seen an explosion of empirical research on economic growth and its determinants, yet many of the central issues of interest remain unresolved. For instance, no consensus has emerged about the relative contributions of capital accumulation and improvements in total factor productivity in accounting for differences in growth across countries and time. Nor is there agreement about the role of increased education or the importance of economic policy. Indeed, results from the many studies on a given issue frequently reach opposite conclusions. And two of the main empirical approaches—growth accounting and growth regressions— have themselves come under attack, with some researchers going so far as to label them as irrelevant to policymaking.