While there is much discussion about the ageing population leaving too few workers to pay for the increasing number of retirees, I wonder if that is the real issue. It seems to me the problem might be whether there will be enough work for even this smaller number.
Technology is changing how we do everything. Fewer and fewer people are engaged in currency transactions making most purchases automated, 3-d printing will soon make a lot of manufacturing ad hoc, auto repair has become almost a "plug and play" occupation with the computer doing all the diagnoses, even security operations have become more and more robotic.
The post-industrial era has meant the increasing decline in the number of people required to do anything. And new technologies are based on minimizing human intervention. We need to understand what that means for the world economy. How do we provide a decent living standard to people we have no jobs for? Do we limit work hours or the number of jobs one person can have at any one time? What effect will fewer working people have on consumption and the rest of the economy? Who will pay for "civilization"?
As with climate change, we can't just react when this stuff becomes reality. We need to start thinking about it now.