efficiency requires a state-dependent division of returns such that, for every state of nature the average and marginal rate of substitution in consumption weighted by individual shareholdings, be the same for holders of preferred stock and for holders of common stock. The rationale for this condition is the following: if one group of shareholders valued future output, conditional on some state, more than other group, it should receive a larger fraction of future output and compensate the other group in terms of current income, and both groups would be bound to gain.