This book is about the distribution of wealth among people, described by statisticians as the size distribution of wealth, and the way that this distribution has changed over time. It provides answers to a host of important questions including, why is the distribution of wealth important and how can it be measured? How unequal is this distribution in practice, and has the degree of inequality changed over time? What factors determine the level of inequality? What criteria can be used to rank alternative distributions of wealth and what instruments are available to a government that wishes to change the distribution? How is the distribution of wealth related to the aggregate amount of wealth? The answers have many dimensions, notably economic, statistical, ethical, political, sociological and legal.