This book is about wealth mobility. It is about how some people get rich while others stay poor. In particular, it is about the paths people take during their lives and how these paths influence how well-off they become. In the 1964 movie I'd Rather Be Rich, people were typical in their willingness to go to great lengths to get rich. In the movie, the goal was to inherit from a dying grandfather, but people have all manner of ways of trying to hit it big. There is a general sense that being rich is better than not being rich, but wealth – and the processes that lead to wealth ownership – may be even more important than most people realize.

Wealth is the things people own, including their homes, savings, investments, real estate, businesses, and vehicles. It is usually measured as net worth, the sum of assets less the sum of debts. Owning wealth has many advantages, from the obvious financial freedom it provides to the even more enduring social and political privileges and power accessible to the wealthy. These advantages and the elusive nature of true wealth make questions about who is rich and why broadly appealing. Dramatic economic changes in recent years, accompanied by rising wealth inequality, have created renewed interest in wealth. These changes have also generated speculation about new patterns in the ways people become wealthy.