 There are mechanisms that encourage individuals to reveal their true valuations of the public good. One is the so-called Groves-Clarke mechanism (after Groves 1973 and Clarke 1971). Here each individual submits a bid, which may be positive or negative, and which may or may not reflect the individual’s true value of the public good (i.e., the reservation price minus the cost). The public good is provided if and only if the sum of bids is at least zero. Apart from the public good, each individual receives a “side payment” calculated as the sum of all other individuals’ bids (which may also be negative, i.e., a tax).