Efficient raffling of public goods

How to provide for a public good is a classic problem, because of the free-rider problem. If you cannot compel users, say, by forced taxation, it is very difficult to recoup the cost of a public good, unless the cost is very low and the benefit to each user very large. That rarely happens. So how can you solve this conundrum when philanthropy is not available?

Jörg Franke and Wolfgang Leininger propose an algorithm based on raffling the cost of the public good. This ideas is due to John Morgan: you create a lottery for the benefit of a socially beneficial public good. Then, people are willing to pay more for the public good. But this is not yet sufficient for the efficient amount of public good. To get there, Franke and Leininger propose an unfair raffle. The raffle tickets are sold at prices that look like Lindahl pricing, but unlike in the Lindahl model, there is no coercion. While there are already many charity raffles that would fit the Morgan model, I cannot think of an unfair public-good raffle in practice, though.