Sustainability constraints versus "optimality" versus intertemporal concern, and axioms versus data

Sustainable, sustained, or survivable development are defined here as distinct "sustainability" constraints on intertemporal distribution, in a context which ignores uncertainty, environmental, and intratemporal concerns. Such constraints are neither self-contradictory; nor redundant, for they can conflict with maximizing the present value of utility ("optimality"); nor inferior, since the axioms underlying "optimality" are ethically arbitrary and refuted by empirical psychological data. Axiomatic arguments may clarify but cannot resolve debates about intertemporal concerns. Data suggest that sustainability constraints are not respected, and that intertemporal welfare functions containing a preference for "sustained improvement" may better reflect what bodies politic mean by sustainability.