To know the entire process of cash creation today, why don’t we produce a hypothetical system of banking institutions. We’re going to concentrate on three banking institutions in this system: Acme Bank, Bellville Bank, and Clarkston Bank. Assume that most banking institutions have to hold reserves add up to 10% of the checkable deposits. The number of reserves banking institutions have to hold is named needed reserves. The book requirement is expressed being a needed book ratio; it specifies the ratio of reserves to checkable deposits a bank must maintain.