On the time consistency of collective preferences
  A dynamic model of collective consumption and saving decisions made by a finite number of agents with constant but different discount rates is developed. Collective utility is a weighted sum of individual utilities with time-varying utility weights. Under standard separability assumptions, it is shown that collective preferences may be nonstationary but still satisfy time consistency. The assumption of time-varying weights is key to balance the need of the group for a changing distribution of consumption among its members over time with their tolerance for consumption fluctuations. 
Luis A. Alcala
math.OC q-fin.EC