Robert Gilpin on equilibrium and decline

Robert Gilpin, War and Change in International Politics (1981), describes the relationship between economic growth and power, like Paul Kennedy's The Rise and Fall of the Great Powers: Economic Change and Military Conflict, 1500-2000. Compared to Kennedy, Gilpin's book is considerably more abstract and concise.

Gilpin describes the dynamics of decline:

Speaking broadly, the national income of a society is distributed into three general sectors: protection; consumption (private and public); productive investment. Protection relates to the costs of national security and the costs of protecting the property rights of citizens. Consumption refers to private and public consumption of goods and services. Investment is that part of the national product that is returned to the productive sector of the economy to increase the efficiency and productivity of land, labor, and, in the modern world, industrial plant.

For a number of reasons that will be discussed later, the historical tendency is for the protection and consumption (private and public) shares of national income to increase as a society ages. This, in turn, means that the share of gross national product reinvested in the economy must of necessity decrease (unless, of course, additional resources can be obtained from other economies). As a consequence, the efficiency and productivity of the productive sector of the economy on which all else rests will decline. If the productive base of the economy erodes, it becomes more difficult to meet the rising demands of protection and consumption without further cutbacks in productive investment, thus further weakening the future economic health of the society. The society enters a downward spiral of rising consumption and declining investment that undermines the economic, military, and political foundations of the state's international position. As a consequence of these developments, the declining power begins to experience what Harold and Margaret Sprout aptly called "the dilemma of rising demands and insufficient resources" (1968).