I was thinking about demographics the other day, in the context of what they mean for economic growth over the next decade or so. One of the reasons growth has been so slow in recent years is simply because of the age mix of the population. Baby boomers are aging and retiring, so they are spending less. The rising millennial generation, on the other hand, has not yet hit its peak earning and spending years. As such, the drag from the boomers offsets the gain from the millennials. It will continue to do so for the next couple of years, but then that will change. The effect of demographics is one of the few things we really can know ahead of time in economics. We know who has been born—and when. After that, it is just a matter of counting.