We compare three different views on the long run efficiencies of emission taxes which include thresholds, and of tradable emission permits where some permits are initially free. The differences are caused by different assumptions about whether thresholds and free permits should be subsidies...

A theoretical, representative agent economy with a depletable resource stock, polluting emissions and productive capital is used to contrast environmental policy, which internalises externalised environmental values, with sustainability policy, which achieves some form of intergenerational...

Exact optimal paths are calculated for two closed, continuous-time economies with explicit functional forms for utility from consumption, and for production from human-made capital and a non-renewable resource. Features of the first economy are non-linear utility, hyperbolic utility discounting...