But Clinton is referring to 'vulnerability dependence'. This is a question of exit costs: how costly would it be for the two parties in an economic transaction to exit the relationship and find alternatives? The side that can do so cheaply has bargaining power, and in a political dispute could threaten the economic relationship as a way of achieving leverage. To use Clinton's Europe-Russia example, if it is easier and cheaper for Russia to find alternative customers for its gas than it is for Europe to find alternative suppliers, Russia has the upper hand.