This article considers the growth of the international testing regime. It discusses sources of growth and empirically examines two related sets of issues: (1) the stability of countries' achievement scores, and (2) the influence of those national scores on subsequent economic development over different time lags. The article suggests that stability over time and across tests has historically been weak but is increasing in the post-1990 era. In addition, the analysis finds little evidence of macro-level effects of test score performance on subsequent economic growth. The article concludes by discussing scenarios that might alter these patterns.