Hegemonic stability theory (HST) is a theory of international relations, rooted in research from the fields of political science, economics, and history. HST indicates that the international system is more likely to remain stable when a single state is the dominant world power, or hegemon.Joshua S. Goldstein. International Relations. New York: Pearson-Longman, 2005. 83, 107. Thus, the end of hegemony diminishes the stability of the international system. As evidence for the stability of hegemony, proponents of HST frequently point to the Pax Britannica and Pax Americana, as well as the instability prior to World War I (when British hegemony was in decline) and the instability of the interwar period (when the American hegemon reduced its presence from world politics).

The key mechanisms in hegemonic stability theory revolve around public goods provision: to resolve collective action problems regarding public goods, a powerful actor who is willing and able to shoulder a disproportionate share of public goods provision is needed. Hegemonic stability may entail self-reinforcing cooperation, as it is in the interest of the hegemon to provide public goods and it is in interest of other states to maintain an international order from which they derive public goods.

Early development Charles Kindleberger is one of the scholars most closely associated with HST; commentators such as Benjamin Cohen regard him as the theory's founder and most influential proponent.Helen Milner. "International Political Economy: Beyond Hegemonic Stability," Foreign Policy, (1998) In his 1973 book The World in Depression: 1929—1939, Kindleberger argued that the economic chaos between World War I and World War II that led to the Great Depression was partly attributable to the lack of a world leader with a dominant economy. Kindleberger's reasoning touched upon more than economics, however: the central idea behind HST suggests that the stability of the global system, in terms of politics, international law, and so on, relies on the hegemon to develop and enforce the rules of that system. Other key figures in the development of hegemonic stability theory include Robert Gilpin and Stephen Krasner.

In his major work, Gilpin theorizes world history as imperial cycles until late modern times and the succession of hegemonies in late modern times when first Britain and later the United States stabilized the international system.Gilpin, Robert, (1981). War and Change in World Politics, Cambridge University Press, p. 145. Gilpin opposes balancing and the balance-of-power theory. He contends that the system naturally goes toward equilibrium. From global war or "hegemonic war" emerges a new hegemon who creates and keeps the new world order with its own set of preferences. This is partly accomplished by providing public goods. In the case of the hegemony of the United States after 1945, there took place attempts at initialising a stable currency by means of the International Monetary Fund, the Bretton Woods system, establishment of the World Bank, security alliances (such as NATO), and democratisation.

Gilpin argues further that in the global system, the more decisive a victory is after the "hegemonic war", the more stable the new system will be. He agrees with Paul Kennedy's view of "imperialistic overstretch" as one of the reasons that hegemons fall. Gilpin adds that all hegemons inevitably fall because at a certain stage expansion exceeds benefits, distribution of power in the system shifts and other states rise and challenge the hegemon. Eventually, a dissatisfied great power that approaches the power of the current hegemon will cause a new global war and the cycle repeats.

Robert Keohane coined the term "Hegemonic stability theory" in a 1980 article. Keohane's 1984 book After Hegemony used insights from the new institutional economics to argue that the international system could remain stable in the absence of a hegemon, thus questioning hegemonic stability theory. John Ruggie's work on embedded liberalism also challenged hegemonic stability theory. He argued that the post-WWII international order was not just held together by material power but through "legitimate social purpose" whereby governments created support for the international order through social policies that alleviated the adverse effects of globalization. John Ikenberry argues that hegemony is not a precondition for international stability, pointing to path dependence and "stickiness" of institutions.

Hegemonic attributes

To rise to hegemonic status, a state must make commitments spanning multiple domains. In the view view of the American grand strategist Christopher Layne, hegemonic states have five defining attributes:

Superior military force is necessary for the ability to forge new international laws and organizations. Insularity provides added security and the potential to project military forces, though in some cases hegemons have not been insular or peninsular. The United States of America, for instance, has become a virtual island. It has two massive seaboards, and its neighbors are long-standing allies, setting it apart from the rest of great powers. Nuclear weapons and superior air force add to its national security. A large and growing economy. Usually, unrivaled supremacy in at least one leading economic or technological sector is necessary. Military and economic powers compose the capability to enforce the rules of the system. The will to lead and to establish a hegemonic regime by enforcing the rules of the system. After World War I, the United States possessed the capacity to lead, but lacked the will to do so. Without the will to force stability on the international system, the United States missed an opportunity to prevent the onset of the Great Depression or World War II. A hegemon must commit to the system, which needs to be perceived as mutually beneficial by other great powers and important state-actors.

Competing theories of hegemonic stability

Research on hegemony can be divided into two schools of thought: the realist school and the systemic school. Each school can be further sub-divided. Two dominant theories have emerged from each school. What Robert Keohane first called the "theory of hegemonic stability",Robert Gilpin. The Political Economy of International Relations. Princeton: Princeton University Press, 1987. 86. joins A. F. K. Organski's Power Transition Theory as the two dominant approaches to the realist school of thought. Long Cycle Theory, espoused by George Modelski, and World Systems Theory, espoused by Immanuel Wallerstein, have emerged as the two dominant approaches to the systemic school of thought.Terry Boswell and Mike Sweat. "Hegemony, Long Waves, and Major Wars: A Time Series Analysis of Systemic Dynamics, 1496-1967," International Studies Quarterly (1991) 35, 124.

Systemic school of thought

According to Thomas J. McCormick, scholars and other experts on the systemic school define hegemony "as a single power's possession of 'simultaneous superior economic efficiency in production, trade and finance.'" Furthermore, a hegemon's superior position is considered the logical consequence of superior geography, technological innovation, ideology, superior resources, and other factors.Thomas J. McCormick. "World Systems," Journal of American History (June, 1990) 77, 128.

Long cycle theory

George Modelski, who presented his ideas in the book, Long Cycles in World Politics (1987), is the chief architect of long cycle theory. In a nutshell, long cycle theory describes the connection between war cycles, economic supremacy, and the political aspects of world leadership.

Long cycles, or long waves, offer interesting perspectives on global politics by permitting "the careful exploration of the ways in which world wars have recurred, and lead states such as Britain and the United States have succeeded each other in an orderly manner." Not to be confused with Simon Kuznets' idea of long-cycles, or long-swings, long cycles of global politics are patterns of past world politics.George Modelski. Long Cycles in World Politics. Seattle: University of Washington Press, 1987.

The long cycle, according to Dr. Dan Cox, is a period of time lasting approximately 70 to 100 years. At the end of that period, "the title of most powerful nation in the world switches hands."Jimmy Myers. "Missouri Western Faculty Discuss Iraq War." St. Joseph News-Press. 2 Mar 2007. Modelski divides the long cycle into four phases. When periods of global war, which could last as much as one-fourth of the total long cycle, are factored in, the cycle can last from 87 to 122 years.George Modelski. Long Cycles in World Politics. Seattle: University of Washington Press, 1987, 102

Many traditional theories of international relations, including the other approaches to hegemony, believe that the baseline nature of the international system is anarchy.Mark Rupert. "Hegemonic Stability Theory. Modelski's long cycle theory, however, states that war and other destabilizing events are a natural product of the long cycle and larger global system cycle. They are part of the living processes of the global polity and social order. Wars are "systemic decisions" that "punctuate the movement of the system at regular intervals." Because "world politics is not a random process of hit or miss, win or lose, depending on the luck of the draw or the brute strength of the contestants," anarchy simply doesn't play a role. After all, long cycles have provided, for the last five centuries, a means for the successive selection and operation of numerous world leaders.George Modelski. Long Cycles in World Politics. Seattle: University of Washington Press, 1987, 100, 135 and 227.

Modelski used to believe that long cycles were a product of the modern period. He suggests that the five long cycles, which have taken place since about 1500, are each a part of a larger global system cycle, or the modern world system.

Under the terms of long cycle theory, five hegemonic long cycles have taken place, each strongly correlating to economic Kondratieff Waves (or K-Waves). The first hegemon would have been Portugal during the 16th century, then the Netherlands during the 17th century. Next, Great Britain served twice, first during the 18th century, then during the 19th century. The United States has been serving as hegemon since the end of World War II.

The traditional view of long cycle theory has evolved somewhat, as Modelski now suggests that Northern and Southern Sung China, Venice and Genoa were each the dominant economic powers during medieval long cycles. However, he does not classify any of these states as world powers. Only when Portugal gained hegemony after 1500 is that distinction made.

Other views of hegemonic stability

Neorealist interpretation

In his book The Tragedy of Great Power Politics John J. Mearsheimer, a Neorealist and offensive realist,2001:4 outlines how the anarchic system that neorealists subscribe to (see Kenneth Waltz for original theory) creates power hungry states who will each attempt to install themselves as regional and global hegemons.Mearsheimer, John, J. 'The Tragedy of Great Power Politics' W. W. Norton & Company, NYC 2001:1-366 The system is created, shaped and maintained by coercion. The hegemon would begin to undermine the institution when it is not in their interests. With the decline of a hegemon, the system descends into instability.

Classical liberal interpretation It is motivated by enlightened self-interest; the hegemon takes on the costs because it is good for all actors, thereby creating stability in the system, which is also in the interests of all actors.

Neoliberal interpretation