The number of people in microregions with low health and income fell by three quarters over the past 20 years. Most of the remaining microregions were in sub-Saharan Africa, but progress was substantial there, too.

In 2000, about 1.1 billion people lived in 10,600 microregions where life spans were short and GDP per capita low—both variables in the bottom 30 percent of the world. How did those places, which appear in orange on our maps, evolve over the last 20 years? Which ones transitioned to greater prosperity and well-being and which ones did not? And where did microregions slip into orange? In this chapter, we examine progress at the bottom of the development spectrum—the last frontier.