In public choice theory, preference revelation (also preference revelation problem) is an area of study concerned with ascertaining the public's demand for public goods. According to some economists, if government planners do not have "full knowledge of individual preference functions", then it is likely that public goods will be under- or over-supplied.When there is no market to induce people to reveal their subjective valuations, economists say that there is a “problem of preference revelation.” When perfect compensation is possible in principle, it may be impossible in fact because of the problem of preference revelation