 However, it is not easy for the government to estimate the demand for a given public good and calculate the appropriate level of taxes. If preferences were observable, the government could charge each citizen according to their marginal benefit (thereby levying so-called “Lindahl taxes”), and an efficient equilibrium (the “Lindahl equilibrium”) would result (Varian 1992: 426; Roberts 1974). But preferences can’t be observed. If they can’t, people have an incentive systematically to understate their reservation prices in the hope that others won’t do the same so they can free-ride on others’ tax contributions. If everyone does that, the public good doesn’t get funded publicly.