Right now, the number of people living on $2 or less a day is more than the entire population of the world in 1950. These 2.7 billion people are not just the world's greatest challenge; they represent an extraordinary market opportunity. By learning how to serve them ethically and effectively, businesses can earn handsome profits while helping to solve one of the world's most intractable problems. The key is what Paul Polak and Mal Warwick call Zero-Based Design: starting from scratch to create innovative products and services tailored for the very poor, armed with a thorough understanding of what they really want and need and driven by what they call 'the ruthless pursuit of affordability.' Polak has been doing this work for years, and Warwick has extensive experience in both business and philanthropy. Together, they show how their design principles and vision can enable unapologetic capitalists to supply the very poor with clean drinking water, electricity, irrigation, housing, education, healthcare, and other necessities at a fraction of the usual cost and at profit margins attractive to investors. Promising governmental and philanthropic efforts to end poverty have not reached scale because they lack the incentives of the market to attract massive resources. This book opens an extraordinary opportunity for nimble entrepreneurs, investors, and corporate executives that will result in not only vibrant, growing businesses but also a better life for the world's poorest people.