Declining population, and as a result of that, a declining economy, for the next hundred years is getting more likely. In fact, most industrialized nation's births are already below replacement level, and the developing world is not far behind. At some point in the near future, the chief problem every country may face will be how to get the birth rate up.
The article doesn’t talk about population. It discusses many other things but primarily focusses on lack of capital formation and over reliance on debt in its place.