If for instance a smaller interest elasticity is used as a criterion of the greater potency of monetary policy (using the familar textbook example) then money will be deemed to be more potent if 'money' defined as m i, rather than m2 or m i plus td, since the m i elasticity with respect to rb is -0.07 whereas that of td is -0.80. These are large differences with quite different rates of monetary expansion being implied in order to bring about a given change in income within a given time period.