Sound taxation? On the use of self-declared value

► In the 16th century, ships passing through the Sound had to pay taxes known as the Sound Dues. ► The King wanted to give Skippers an incentive to declare the true value. ► He therefore reserved the right to purchase the cargo at the declared value. ► We give a game-theoretic treatment of this rule. ► We show that it allows the authorities to effectively implement a given tax rate.