The tendency of the rate of profit to fall (TRPF) is a hypothesis in economics and political economy, most famously expounded by Karl Marx in chapter 13 of Capital, Volume III. Economists as diverse as Adam Smith, John Stuart Mill, David Ricardo and Stanley Jevons referred explicitly to the TRPF as an empirical phenomenon that demanded further theoretical explanation, yet they each differed as to the reasons why the TRPF should necessarily occur.
Now, I have some years trained as an economist; but, find the whole fuss around the TRPF somewhat strange. Marx lived in a time of a non-fiat economy. The inherent value of one kopiejek or what have you was based on how much bread it could exchange. Nowadays money is defined to be a unit of account maintained by trust in the FED. Hence, inflation targeting.
So, did Marx really miss the memo about credit? Can someone help me better understand where am I getting this concept wrong as so many think this is the cornerstone of Marxian economics.