The Bottom Billion: Why the Poorest Countries are Failing and What Can Be Done About It is a 2007 book by Paul Collier, Professor of Economics at Oxford University, exploring the reasons why impoverished countries fail to progress despite international aid and support. In the book Collier argues that there are many countries whose residents have experienced little, if any, income growth over the 1980s and 1990s. On his reckoning, there are just under 60 such economies, home to almost 1 billion people.