Perhaps just a technicality, but: to satisfy the transversality condition, an infinitely lived agent has to have a discount rate of at least r (1-σ). So if σ >1—i.e. if the utility function is more concave than log—then the time preference rate can be at least a bit negative.
Perhaps just a technicality, but: to satisfy the transversality condition, an infinitely lived agent has to have a discount rate of at least r (1-σ). So if σ >1—i.e. if the utility function is more concave than log—then the time preference rate can be at least a bit negative.