Logrolling has one necessary condition: benefits from the public activity must be significantly more concentrated or localized than the costs. In economics, decisions are made at the margin. Logrolling depends on the reality that the marginal benefit (or utility) of at least some elected officials, or the citizenry, will increase when the legislation is passed (Buchanan and Tullock 1962). Any economist will consider the immediate opportunity cost of the logrolling procedure within the legislative body, as well as the external cost of the vote (the cost to enact and see the bill through to fruition).