Investor pressure could drive down greenhouse gas emissions. Tippapatt/iStock/Getty Images PlusAbout 10 years ago, a very thick book written by a French economist became a surprising bestseller. It was called “Capital in the 21st Century.” In it, Thomas Piketty traces the history of income and wealth inequality over the past couple of hundred years. The book’s insights struck a chord with people who felt a growing sense of economic inequality but didn’t have the data to back it up. I was one of