  Political power in the international context can be characterized as a
fluid-like substance that circulates through a network of nation states. States
can possess it as a stock quantity, reflected by their material capacity or
national wealth; and they can transfer it as a flow quantity, through
constructive or destructive action. Constructive activities like trade increase
a state's power, while destructive ones like violent conflict reduce it. In
this paper, we quantify these assertions to a first approximation using
economic and military data, parameterizing a mathematical model that can
forecast the evolution of power in the international system.
