Is a secondary currency essential? On the welfare effects of a new currency

The coexistence of cash and digital currencies constitutes a system of parallel currencies. This paper tackles the question whether a new (digital) currency is essential: Does a new currency allow for a better resource allocation even if a fully accepted currency is in circulation and still remains in circulation? Using the dual currency search model of Kiyotaki and Wright (1993), we show how the introduction of a secondary currency affects average utility. There is some scope for a welfare improvement, the welfare effect depends on differences in returns and costs, and, in particular, the fraction of cash traders who will be replaced by digital money traders.