Of the roughly 7 billion people in the world, more than 75 percent live in developing countries, and one issue of economic concern in many of these countries is that of population growth. In the summary report of the Population Reference Bureau's 2008 World Population Data Sheet, PRB president Bill Butz made the following comment: "Nearly all of world population growth is now concentrated in the world's poorer countries. Even the small amount of overall growth in the wealthier nations will largely result from immigration." Explain how rapid population growth can limit a nation's productivity. Are there any ways in which population growth can have a positive economic effect? Explain. Source: "2008 World Population Data Sheet," Population Reference Bureau, August 19, 2008.