It think that's why most central banks are showing interest in distributed ledgers for traditional currencies, so that the flow of cash actually become visible.

It think that's why most central banks are showing interest in distributed ledgers for traditional currencies, so that the flow of cash actually become visible. Basically it is well known that the economy is a gigantic graph and that graph theory might help answer fundamental questions about it. The issue is that you need a massive amount of data to have a somewhat accurate model. The central banks do have some data (none on cash tough) as banks have some reporting requirements but generally those data are available only in aggregate and in economics (or basically any forecasting activity) the devil is in the details.