You can find the answer here https://en.wikipedia.org/wiki/Tendency_of_the_rate_of_profit_to_fall https://en.wikipedia.org/wiki/Tendency_of_the_rate_of_profit.

You can find the answer here https://en.wikipedia.org/wiki/Tendency_of_the_rate_of_profit_to_fall https://en.wikipedia.org/wiki/Tendency_of_the_rate_of_profit... This is the first thing that came to my mind as well...the current data on falling rentier rates, crises of political economy etc. makes sense in light of that old model.