Exchange rate changes, including formal devaluation or revaluation, which lead to changes in the aggregate operational costs and/or revenues of the shipping lines members of a conference relating to their operations within the conference provide a valid reason for the introduction of a currency adjustment factor or for a change in the freight rates. The adjustment or change shall be such that in the aggregate the member lines concerned neither gain nor lose, as far as possible, as a result of the adjustment or change. The adjustment or change may take the form of currency surcharges or discounts or of increases or decreases in the freight rates.