A capitalist system is built on the idea that holders of capital actually deploy that capital, rather than horde it.
If capital holders don’t actually deploy that capital and compete with each other, then you don’t have a capitalist system anymore. You have a feudal system, where asset holders extract resources through rents, rather than capital deployment and risk taking.
"Is the capital being deployed for rent seeking or for taking economically useful risks?" is a judgement call. You won't find it listed in a FRED time series.
When every industry is on a multi-decade streak of consolidation, when McDonalds is about land speculation rather than serving food, farming is about land ownership rather than growing food, airlines are about credit cards rather than transportation, it's not unreasonable to believe that a substantial amount of capital is being deployed towards rent-seeking rather than economically useful risk taking.
If capital holders don’t actually deploy that capital and compete with each other, then you don’t have a capitalist system anymore. You have a feudal system, where asset holders extract resources through rents, rather than capital deployment and risk taking.