I have to wonder if these kind of historical comparisons are useful. The market seems so much different than it did prior to 1940 (in my totally naive bystander opinion). 100 years ago you didn't have:

- A diverse economy with many different verticals.

- Globalization of trade

- Massive pension funds with long term holdings

- Average citizens investing capital in other's people production.

- Easy access to trading/information and safer investments like mutual funds and ETFs.

- A giant swath of humans employed in finance all trying to make money and help the market self correct.

- Automated trading that benefits from (and probably creates) minor turbulence to constantly skim money.

What hasn't changed:

- Human psychology

- Economic feedback cycles and interdependence

The market will crash again, but I don't think you can infer too much from the market 100 years ago even as an average.