Two agents must select one of three alternatives. Their ordinal rankings are commonly known and diametrically opposed. Efficiency requires choosing the alternative the agents rank second whenever the weighted sum of their von Neumann Morgenstern utilities is higher than under either agent's...

The paper introduces a notion of complementarity (substitutability) of two signals which requires that in all decision problems each signal becomes more (less) valuable when the other signal becomes available. We provide a general characterization which relates complementarity and...