On VoxEU, Clemens Jobst and Helmut Stix argue that

… cash balances for transactions comprise only a modest share of overall cash demand (a rough estimate of 15% might be a good guess across richer economies). … changes in currency in circulation are dominated by motives like hoarding. While transaction demand is reasonably well researched … still too little is known about non-transaction demand in general, and recent increases in particular.