It's appropriate that Gates reviewed the book, because he and his philanthropic foundation are actually mentioned to buttress Piketty's argument. After he became a very, very rich man, Gates stopped laboring and focused instead on giving away his money. Yet, more than a decade later, his wealth has actually skyrocketed. In 1998, Gates' net worth was valued at $50 billion. By October 2014, that number had increased nearly 60 percent to $79.3 billion, despite his having given away tens of billions of dollars.