I have a theory. The last 100 years has seen govt spending as percent of gdp increase to ever greater levels. People are expecting more and more handouts and no one wants to pay for it. Without the ability to pay for it via taxes, the govt will eventually have to default on it's currency and thus real returns on fixed income/bonds will have to become increasingly negative.

Their article already shows a slight widening between bonds/equities post 1950. My theorey is that for the next 100 years, we'll see a much larger widening between the returns of bonds and equities as more and more governments default on their currency. Thoughts?

EDIT: the article I referenced was the one the other poster mentioned: https://economics.harvard.edu/files/economics/files/ms28533....

Also, equity returns should in the long term be equal to Producivity per capita + population growth + inflation + dividends. And If you look at each of those for the last 100 years and the next 100 years for the US, you'll see a pattern. Pop growth down to 0.4 from 1.3. Per capita growth down several percent in the last 20 years vs the 100 years before that and with current PEs where they are, dividends are down to 1.3% from a historical 4.5%. Translation: Future equity returns will be much much closer to inflation than they have been in the past.