Under such circumstances, for Friedman, two motives exist for a consumer unit to spend more or less on consumption than its income: The first is to smooth its consumption expenditures through appropriate timing of borrowing and lending; and the second is either to realize interest earnings on deposits if the relevant rate of interest is positive, or to benefit from borrowing if the interest rate is negative.
In such situations, Friedman identifies two reasons why a consumer unit might spend more or less than its income:  First, it can manage its spending by strategically timing borrowing and lending; second, it can either earn interest on deposits if the interest rate is positive or benefit from borrowing if the interest rate is negative.