We derive a measure of national income, defined in terms of maximum su
stainable per capita consumption. If population and interest rates are
constant, the income generated by natural resource extraction is the
return on resource wealth, defined as the present value of future reso
urce rents. With a growing population or declining interest rate, sust
ainability requires net increases in wealth over time. The income fi o
m extraction of nonrenewable resources can exceed resource rents, cont
rary to the conclusions of El Serafy (1989) and Repetto et al. (1989).
Finally, we present an example illustrating the hazard of consuming t
he full increment of Hicksian income.