The paper explains how Thomas Piketty's book looks at how rich people spending more money than the economy grows affects wealth accumulation. It uses a mix of old economic ideas to show that Piketty's theory makes more sense than the usual way of thinking about it. The data shows that even though the rich are getting richer, wealth isn't getting more concentrated. And even though profits are up, growth isn't. The paper suggests that in today's world, it's more about spending money than saving it.