This paper studies the restrictions on consumption, portfolio choice, and social discounting implied by a sustainability constraint, that utility should not be expected to decline over time, in an economy with risky investment opportunities. The sustainability constraint does not distort...

We view sustainability as a requirement that welfare should not be expected to decline over time. We impose this requirement as a prior constraint on the consumption-savings-investment problem, and study its implications for saving, risky investment, and the social discount rate. The constraint...