For the U.S. this age ratio will probably stay at around 0.5, which means stock valuations can’t go exorbitantly high like in the NASDAQ bubble of 2000. Also take into account that we live longer, so the higher age groups will be more populated in the future. I’d say the P/E ratio will average at 15-20. So keep your eye on these population pyramid charts and I invite you to look at charts from other countries as well and draw your own conclusions.
This is the chart for Europe, which looks worse than the U.S, because the baby boom generation is going for retirement.
And China, which has the same problem, but to a lesser extent as there are still many young people coming into the workforce.