If we suppose a state capable of living on itself, the quantity of money it would be necessary to put into circulation would depend upon several variables: the quantity of merchandise entering the exchange system; the portion of that merchandise which, being neither distributed nor paid for by barter, must at some moment during its journey be represented by money; the quantity of metal for which signed paper may be substituted; and, finally, the rhythm according to which payments must be made: it is not a matter of indifference, as Cantillon points out, whether workers are paid by the week or the day, or whether rents fall due at the end of every year rather than, as is customary, at the end of every quarter.