The Next 4 Billion: Market Size and Business Strategy at the Base of the Pyramid is a timely and valuable contribution by the team of WRI (Allen L. Hammond, William J. Kramer, Robert S. Katz, Julia T. Tran, Courtland Walker). This reports gives a detailed economic portrait of the BOP based on recorded incomes and expenditures and an overview of sector-specific business strategies from successful enterprises operating in the BOP markets. It is full of data and information that is needed for the private sector which is currently increasing its engagement to this large segment.