We develop a model that shows how the currency denomination of a country's imports influences the funding structure of its banking system, and in turn, the currency composition of its central bank's reserve holdings. The link between the dollar's role in bank funding and its role as a central bank reserve currency is stronger when the country's fiscal capacity is limited, and when exchange rates are volatile. In the data, there is a pronounced cross-country relationship between the fraction of imports that are dollar invoiced, and the fraction of central-bank foreign-exchange reserves that are held in dollars.
The Currency Composition of Foreign Exchange Reserves: Retrospect and Prospect