This was first discussed here: In this context, "efficient" means "on the efficient frontier " while "inefficient" means "not on the efficient frontier." The construction of efficient shopping lists involves the construction of two efficient frontiers. One represents efficiency from an individual consumer's point of view. The other represents the pub wan movement's point of view. It is assumed that the individual consumer wants the maximum bang (or other desireable quantity, and/or the minimum amount of undesireable quantities) for the minimum buck (price). This minimization and maximization stuff constitutes the maxhi schema. It is assumed that the pubwan movement wants opportunities to fill in informational gaps in its database, and take (vicariously, by way of its volunteers) "field tri