An ideal planner would follow the original Samuelson rule to undertake each and every public project, program or activity up to the point where the sum of its marginal benefits is just equal to its marginal cost. Actual governments modify the rule in response to the marginal cost of public funds...

An indivisible good is an ideal type with interesting properties and strong implications about public policy. It is a good - such as a heart transplant or a treatment for AIDS - that must be consumed in a fixed amount or not at all. The community's demand curve for an indivisible good is a...