<p>This paper examines the aggregate economic performance of 143 countries from 1990 to 2019. Fully nonparametric methods are used to estimate changes in total factor productivity. Recently-developed statistical results are employed for inference and to test hypotheses about model structure. We find that productivity increased by 83 percent on average from 1990 to 2019, with larger gains among low income countries. In addition, we find evidence that productivity growth slowed among high, middle and low-income countries in the 10-year period following the 2008 financial crisis relative to growth over the ten-year period before the crisis. This finding is consistent with what others in the growth literature have found. Finally, our results indicate that low-income countries are less efficient than high- or middle-income countries.</p>