Driving with Eyes on the Rear-View Mirror—Why Weak Sustainability Is Not Enough

Abstract

Weak sustainability, WS, attempts a comprehensive notion of sustainability, sustaining human welfare directly, or equivalently, sustaining inclusive wealth, IW, sufficient to sustain welfare. Sustainability is, in principle, forever, and accordingly, IW is conceived and assessed in a very long-term context. Given that future outcomes are unobservable, IW assessments are conducted in terms of expectations. However, this introduces pervasive circular reasoning: the calculated value of IW assumes that our expectations will be met, but that is the question. Optimistic expectations (for example) increase calculated IW, which, in turn, increases our confidence that our society is on a sustainable path. Given the logical difficulties of projecting IW into the future, analysts resort to tracking IW at regular intervals through the recent past. This reduces, but does not eliminate, the circularity problem. The signals from tracking IW are less than perfect from a policy perspective: they are too aggregate, perhaps masking impending crises regarding particular resources until it is too late; and too dependent on imperfect markets; and they document the recent past, so policy managers are always playing catch-up. WS-based sustainability policy frameworks include WS-plus, which invokes ad hoc strong sustainability, SS, patches to address threatened resource crises. It may also be possible to allow a degree of WS flexibility for individual jurisdictions within the constraints of a global safe operating space, SOS.