William Baumol published an enlightening study of long-run trends in productivity. His data came from 72 countries and reached back to 1870.8 The study focused on what Baumol calls the process of convergence. According to this process, the countries with the lowest levels of productivity in 1870 have had the highest rates of improvement over the years, while the most productive countries in 1870 have exhibited the slowest rates of improvement—the peapods at work again, in other words.
