OXFORD – When one state is preponderant in power resources, observers often refer to the situation as hegemonic. Today, many pundits argue that other countries’ rising power and the loss of American influence in a revolutionary Middle East point to the decline of "American hegemony.” But the term is confusing.

For one thing, possession of power resources does not always imply that one can get the outcomes one prefers. Even the recent death of Osama bin Laden at the hands of United States special forces does not indicate anything about American power one way or the other.

To see why, consider the situation after World War II. The US accounted for more than one-third of global product and had an overwhelming preponderance in nuclear weapons. Many considered it a global hegemon.

Nonetheless, the US was unable to prevent the "loss” of China, "roll back” communism in Eastern Europe, prevent stalemate in the Korean War, defeat Vietnam’s National Liberation Front, or dislodge the Castro regime in Cuba.

Even in the era of alleged American hegemony, studies show that only one-fifth of America’s efforts to compel change in other countries through military threats were successful, while economic sanctions worked in only half of all cases. Yet many believe that America’s current preponderance in power resources is hegemonic, and that it will decline, like that of Britain before it. Some Americans react emotionally to that prospect, though it would be ahistorical to believe that the US will have a preponderant share of power resources forever.

But the term "decline” conflates two different dimensions of power: absolute decline, in the sense of decay or loss of ability to use one’s resources effectively, and relative decline, in which the other states’ power resources become greater or are used more effectively. For example, in the seventeenth century, the Netherlands flourished domestically but declined in relative power as other states grew in strength. Conversely, the Western Roman Empire did not succumb to another state, but instead to internal decay and swarms of barbarians. Rome was an agrarian society with low economic productivity and a high level of internecine strife.

While the US has problems, it hardly fits the description of absolute decline in ancient Rome, and the analogy to British decline, however popular, is similarly misleading. Britain had an empire on which the sun never set, ruled more than a quarter of humankind, and enjoyed naval supremacy.

But there are major differences in the relative power resources of imperial Britain and contemporary America. By World War I, Britain ranked only fourth among the great powers in terms of military personnel, fourth in GDP, and third in military spending. The costs of defense averaged 2.5-3.4% of GDP, and the empire was ruled in large part with local troops.

In 1914, Britain’s net export of capital gave it an important financial kitty to draw upon (though some historians consider that it would have been better to have invested the money in domestic industry). Of the 8.6 million British forces in WWI, nearly one-third were provided by the overseas empire.

With the rise of nationalism, however, it became increasingly difficult for London to declare war on behalf of the empire, the defense of which became a heavier burden. By contrast, America has had a continental-scale economy immune from nationalist disintegration since 1865. For all the loose talk of American empire, the US is less tethered and has more degrees of freedom than Britain ever had.

Indeed, America’s geopolitical position differs profoundly from that of imperial Britain: while Britain faced rising neighbors in Germany and Russia, America benefits from two oceans and weaker neighbors.

Despite these differences, Americans are prone to cycles of belief in decline. The Founding Fathers worried about comparisons to the decline of the Roman republic. Moreover, cultural pessimism is very American, extending back to the country’s Puritan roots. As Charles Dickens observed a century and a half ago, "if its individual citizens, to a man, are to be believed, [America] always is depressed, and always is stagnated, and always is in an alarming crisis, and never was otherwise.”

More recently, polls showed widespread belief in decline after the Soviet Union launched Sputnik in 1957, then again during the Nixon-era economic shocks in the 1970’s, and after Ronald Reagan’s budget deficits in the 1980’s. At the end of that decade, American’s believed the country was in decline; yet, within a decade, they believed that the US was the sole superpower. Now many have gone back to believing in decline.

Cycles of declinism tell us more about American psychology than about underlying shifts in power resources. Some observers, such as the Harvard historian Niall Ferguson, believe that "debating the stages of decline may be a waste of time – it is a precipitous and unexpected fall that should most concern policy makers and citizens.” Ferguson believes that a doubling of public debt in the coming decade cannot erode US strength on its own, but that it could weaken a long-assumed faith in America’s ability to weather any crisis.

Ferguson is correct that the US will have to come to terms with its budget deficit to maintain international confidence, but, as I show in my book The Future of Power, doing so is within the range of possible outcomes. America enjoyed a budget surplus only a decade ago, before George W. Bush’s tax cuts, two wars, and recession created fiscal instability.

The US economy is still ranked near the top in competitiveness by the World Economic Forum, and the political system, in its own messy way, has slowly begun to wrestle with the necessary changes.

Some believe a political compromise between Republicans and Democrats can be reached before the 2012 election; others suggest an agreement is more likely after the election. Either way, fuzzy statements about hegemonic decline would again prove misleading.

Joseph S. Nye, Jr. is a professor at Harvard and author of The Future of Power.

Copyright: Project Syndicate, 2011.