A fundamental advantage of a regime withfixed exchange rates, in one view, is that it implies monetary integration.International money in international economy is seen as crucially beneficial,for the same reason as that justifying monetary integration at the level ofindividual countries, namely, the existence of a common standard of value andmedium of payment to express economic contracts and regulate transactions. Thebenefits that may result from a system with stable exchange rates should becompared with the costs due to the constraints that such a systemimposes on sovereignty, that is, the ability of countries to act ontheir own instead of under the instructions of another. Clearly,sovereignty is constrained under irrevocable fixed exchange rates (e.g.countries lose control of monetary policy in their own economy as the interestrate cannot deviate from the world interest rate, unless constraints areimposed on convertibility.