We live in a culture obsessed with doing something. Track your sleep. Optimize your workouts. Measure everything, always. Naturally, we bring that same mentality to our money, which is understandable given the stakes. But when it comes to your portfolio, is all that activity actually helping? New research offers a surprisingly clear answer. In today's email: Warren Buffett's memorable case for "doing nothing" The new 50-year study that put inactivity to the test Why doing nothing is an active...