今天学了public good and common resources.在 public good 这一部分下面,讲了一个the free-rider problem.书里有一句话:a free-rider problem arises when the number of beneficiaries is large and exclusion of any one of them is impossible.我不明白,free-rider的问题是在public good中出现的?还是说,在别的地方出现,而因为它的出现,政府介入,使这个商品变成了public good?还是什么其它的解释~~谢谢!