 Another argument used by anarcho-capitalists states that, unlike voluntary transactions, no demonstrated preference has been made by the taxpayer; so they believe there is no objective way of showing that they are receiving a service they want and need, at a price that is fair.According to David D. Friedman, "Medieval Icelandic institutions have several peculiar and interesting characteristics; they might almost have been invented by a mad economist to test the lengths to which market systems could supplant government in its most fundamental functions.