  The force of each consideration has been demonstrated in the economics literature. It has been shown in the context of a simple model that if production requires produced capital and exhaustible resources, then optimum consumption declines to zero in the long run if future well-beings are discounted at a positive rate (Dasgupta and Heal, 1974), but increases indefinitely if we follow Ramsey in not discounting future well-beings (Solow, 1974b). The exercises tell us that the long-run features of optimum saving policies depend on the relative magnitudes of the rate at which future well-beings are discounted and the long-term productivity of capital assets.