AMERICA IS in unprecedented decline. The self-inflicted wounds of the Iraq War, growing government debt, increasingly negative current-account balances and other internal economic weaknesses have cost the United States real power in today's world of rapidly spreading knowledge and technology. If present trends continue, we will look back at the Bush administration years as the death knell for American hegemony.

Since the cold war, the United States has maintained a vast array of overseas commitments, seeking to ensure peace and stability not just in its own neighborhood-the Americas-but also in Europe and Asia, along with the oil-rich Persian Gulf (as well as other parts of the world). Simply maintaining these commitments requires enormous resources, but in recent years American leaders have pursued far more ambitious goals than merely maintaining the status quo. The Bush administration has not just continued America's traditional grand strategy, but pursued ambitious objectives in all three major regions at the same time-waging wars in Iraq and Afghanistan, seeking to denuclearize North Korea and expanding America's military allies in Europe up to the borders of Russia itself.

For nearly two decades, those convinced of U.S. dominance in the international system have encouraged American policy makers to act unilaterally and seize almost any opportunity to advance American interests no matter the costs to others, virtually discounting the possibility that Germany, France, Russia, China and other major powers could seriously oppose American military power. From public intellectuals like Charles Krauthammer and Niall Ferguson to neoconservatives like Paul Wolfowitz and Robert Kagan, even to academicians like Dartmouth's William Wohlforth and Stephen Brooks, all believe the principal feature of the post-cold-war world is the unchallengeable dominance of American power. The United States is not just the sole superpower in the unipolar-dominance school's world, but is so relatively more powerful than any other country that it can reshape the international order according to American interests. This is simply no longer realistic.

For the past eight years, our policies have been based on these flawed arguments, while the ultimate foundation of American power-the relative superiority of the U.S. economy in the world-has been in decline since early on in the Bush administration. There is also good reason to think that, without deliberate action, the fall of American power will be more precipitous with the passage of time. To be sure, the period of U.S. relative decline has been, thus far, fairly short. A healthy appreciation of our situation by American leaders may lead to policies that could mitigate, if not rectify, further decline in the foreseeable future. Still, America's shrinking share of world economic production is a fact of life and important changes in U.S. grand strategy are necessary to prevent the decline in America's global position from accelerating.

Although the immediate problems of war in Iraq and Afghanistan, al-Qaeda's new sanctuary in western Pakistan, Iran's continued nuclear program and Russia's recent military adventure in Georgia are high-priority issues, solutions to each of them individually and all of them collectively will be heavily influenced by America's reduced power position in the world. Most important, America's declining power means that the unipolar world is indeed coming to an end, that major powers will increasingly have the strength to balance against U.S. policies they oppose and that the United States will increasingly face harsh foreign-policy choices. Like so many great powers that have come and gone before, our own hubris may be our downfall.

FROM ROME, Imperial China, Venice, Spain, France, Great Britain and the Soviet Union to the United States today, the rise and fall of great nations has been driven primarily by relative economic strength. As Paul Kennedy so ably describes in his classic The Rise and Fall of Great Powers, the more international commitments a state has, the more its power matters and hence the more relative economic strength it needs.

Although scholars have long debated its nuances, the basic definition of power in international politics is simple: power is the aggregate resources a state has at its disposal to achieve its aims, the most important of which are to defend its national interests, both at home and abroad.¹ But it is not only how much power a state has that matters. It is also how much power a state has relative to other states. This is true in any rough-and-tumble environment. A Ford Explorer is a powerful vehicle-unless it collides with a Mack Truck. In international politics, power does not ensure success. But, power certainly helps.

At any given moment, U.S. power is heavily dependent on the size and quality of its military forces and other current power assets. A successful grand strategy, however, must work for the long haul and so depends on the power a state is able to produce in the future.

Over time, America's power is fundamentally a result of its economic strength. Productive capacity-defined by indicators such as wealth, technology and population size-is a prerequisite for building and modernizing military forces. The United States, like any state, may choose to vary the degree to which its productive capacities are used to create military assets. But it is the economy as a whole that constrains the choice. And the size of the economy relative to potential rivals ultimately determines the limits of power in international politics. Major assessments of this relative position have long turned heavily on a single statistic: America's share of world economic product.

Advocates of extending America's unipolar dominance are well aware of the central importance of the economic foundations of American power and routinely present detailed statistics on the U.S. share of world product. The basic notion is simple: take U.S. domestic product in any year and divide it by the aggregate total of the gross domestic product of all states in the world. To measure gross domestic product, the unipolar-dominance school prefers to compare every country's output in current-year U.S. dollars, a method that tends to show America is much further ahead of other countries than alternative measures. Indeed, the most recent call for America to exploit its hegemonic position (published in 2008) rests on the presumption of U.S. dominance based on the current-year dollar figures.² By this metric, in 2006 the United States had 28 percent of world product while its nearest most likely competitor, China, had 6 percent. Looks pretty good for America, right?

Alas, single-year "snapshots" of America's relative power are of limited value for assessing the sustainability of its grand strategy over many years. For grand-strategic concerns-especially how well the United States can balance its resources and foreign-policy commitments-the trajectory of American power compared to other states is of seminal importance.

For the sake of argument, let us start with the unipolar-dominance school's preferred measure of American hegemony, but look at the trajectory of the data over time. According to GDP figures in current U.S. dollars from the International Monetary Fund (IMF), the United States increased its share of world production during the 1990s, reached its apogee in 2000, and then began to steadily lose ground during the eight years of the Bush administration, with its relative power ultimately falling by nearly a quarter in the first decade of the twenty-first century. At the same time, the relative power of China, the state many consider America's most likely future rival, has grown consistently. If we look out as far as the IMF can see (2013), things get even worse-with the United States expected to continue declining and China to continue rising. The United States has been going through the first decade of the twenty-first century not stronger than before, but substantially weaker.

How good are the numbers? Economists commonly use two other methods to calculate GDP, constant-dollar calculations and purchasing power parity.³ Although each offers advantages and disadvantages, for our purposes what matters is that they form a lower bound of America's relative decline. And regardless of the metric, the trend is the same. Again using IMF figures, Table 2 shows the trajectory of the share of world product for the United States and China using both alternative measures.

Simply put, the United States is now a declining power. This new reality has tremendous implications for the future of American grand strategy.

THE EROSION of the underpinnings of U.S. power is the result of uneven rates of economic growth between America, China and other states in the world. Despite all the pro-economy talk from the Bush administration, the fact is that since 2000, U.S. growth rates are down almost 50 percent from the Clinton years. This trajectory is almost sure to be revised further downward as the consequences of the financial crisis in fall 2008 become manifest.

As Table 3 shows, over the past two decades, the average rate of U.S. growth has fallen considerably, from nearly 4 percent annually during the Clinton years to just over 2 percent per year under Bush. At the same time, China has sustained a consistently high rate of growth of 10 percent per year-a truly stunning performance. Russia has also turned its economic trajectory around, from year after year of losses in the 1990s to significant annual gains since 2000.

Worse, America's decline was well under way before the economic downturn, which is likely to only further weaken U.S. power. As the most recent growth estimates (November 2008) by the IMF make clear, although all major countries are suffering economically, China and Russia are expected to continue growing at a substantially greater rate than the United States.

True, the United States has not lost its position as the most innovative country in the world, with more patents each year than in all other countries combined. However, the ability to diffuse new technology-to turn chalkboard ideas into mass-produced applications-has been spreading rapidly across many parts of the globe, and with it the ultimate sources of state power-productive capacities.

America is losing its overwhelming technological dominance in the leading industries of the knowledge economy. In past eras-the "age of iron" and the "age of steel"-leading states retained their technological advantages for many decades.⁴ As Fareed Zakaria describes in his recent book, The Post-American World, technology and knowledge diffuse more quickly today, and their rapid global diffusion is a profound factor driving down America's power compared to other countries. For instance, although the United States remains well ahead of China on many indicators of leading technology on a per capita basis, this grossly under-weights the size of the knowledge economy in China compared to America. Whereas in 2000, the United States had three times the computer sales, five times the internet users and forty times the broadband subscribers as China, in 2008, the Chinese have caught or nearly caught up with Americans in every category in the aggregate.⁵ The fact that the United States remains ahead of China on a per capita basis does matter-it means that China, with more than four times the U.S. population, can create many more knowledge workers in the future.

So, how much is U.S. decline due to the global diffusion of technology, U.S. economic weaknesses under Bush or China's superior economic performance?

Although precise answers are not possible, one can gain a rough weighting of the factors behind America's shrinking share of world production by asking a few simple counterfactual questions of the data. What would happen if we assumed that the United States grew during the Bush years at the same rate as during Clinton's? What would have happened had the world continued on its same trajectory, but we assume China did not grow at such an astounding rate? Of course, these are merely thought experiments, which leave out all manner of technical problems like "interaction effects." Still, these back-of-the-envelope approximations serve as useful starting points.

The answers are pretty straightforward. Had the American economy grown at the (Clinton) rate of 3.7 percent per year from 2000 to 2008 instead of the (Bush) rate of 2.2 percent, the United States would have had a bigger economy in absolute terms and would have lost less power relative to others. Assuming the rest of the world continued at its actual rate of growth, America's share of world product in 2008 would have risen to 25.2 percent instead of its actual 23.1 percent.⁶ When compared to the share of gross world product lost by the United States from 2000 to 2008-7.7 percent-the assumed marginal gain of 2.1 percent of world product amounts to some 27 percent of the U.S. decline.

How much does China matter? Imagine the extreme case-that China had not grown, and the United States and the rest of the world continued along their actual path of economic growth since 2000. If so, America's share of world product in 2008 would be 24.3 percent, or 1.2 percent more than today. When compared to the share of world product lost by the United States from 2000 to 2008-7.7 percent-the assumed marginal gain of 1.2 percent of world product accounts for about 15 percent of the U.S. decline.

These estimates suggest that roughly a quarter of America's relative decline is due to U.S. economic weaknesses (spending on the Iraq War, tax cuts, current-account deficits, etc.), a sixth to China's superior performance and just over half to the spread of technology to the rest of the world. In other words, self-inflicted wounds of the Bush years significantly exacerbated America's decline, both by making the decline steeper and faster and crowding out productive investment that could have stimulated innovation to improve matters.

All of this has led to one of the most significant declines of any state since the mid-nineteenth century. And when one examines past declines and their consequences, it becomes clear both that the U.S. fall is remarkable and that dangerous instability in the international system may lie ahead. If we end up believing in the wishful thinking of unipolar dominance forever, the costs could be far higher than a simple percentage drop in share of world product.

THE UNITED States has always prided itself on exceptionalism, and the U.S. downfall is indeed extraordinary. Something fundamental has changed. America's relative decline since 2000 of some 30 percent represents a far greater loss of relative power in a shorter time than any power shift among European great powers from roughly the end of the Napoleonic Wars to World War II. It is one of the largest relative declines in modern history. Indeed, in size, it is clearly surpassed by only one other great-power decline, the unexpected internal collapse of the Soviet Union in 1991.

Most disturbing, whenever there are major changes in the balance of power, conflict routinely ensues. Examining the historical record reveals an important pattern: the states facing the largest declines in power compared to other major powers were apt to be the target of opportunistic aggression. And this is surely not the only possible danger from relative decline; states on the power wane also have a history of launching preventive wars to strengthen their positions. All of this suggests that major relative declines are often accompanied by highly dangerous international environments. So, these declines matter not just in terms of economics, but also because of their destabilizing consequences.

Tsarist Russia presents the first case in point. Compared to other great powers on the European continent, its power declined the most during the mid-nineteenth century. And, it became the target of opportunistic aggression by the state with the greatest rising power, Great Britain, during the Crimean War (1854-1856). Indeed, the consequences of Russia's decline were not fully recognizable until the war itself. Though Russia was still a great power and the war cost Britain and France more than expected, Russia emerged the clear loser. Russia's inability to defend the status quo in the Crimea confirmed its grand-strategic weaknesses, and ultimately left it worse-off than had it anticipated its vulnerabilities and sought to negotiate a reduction in its military commitments to the region peacefully. Considering that the Crimea conflict left Russia with fairly gaping wounds, and that even its slow 10 percent decline in relative power over twenty years left the country bruised and battered, one might wonder how our far more rapid descent might play out.

Meanwhile, similar destabilization occurred in the two decades before World War I and before World War II, when France and Great Britain were declining European powers. In both instances, France and Britain became targets of opportunistic aggression by one of the strongest rising powers in the region: Germany. And as a small cottage industry of scholarship suggests, Germany's fairly modest relative declines compared to Russia prior to World War I and the Soviet Union prior to World War II encouraged German leaders to wage preventive wars. Again, these declines occurred as another power was concomitantly rising (Germany in the case of France and Britain, and Russia-later the Soviet Union-relative to Germany). Of course, this only served to increase the danger. But again, these rises and falls were less precipitous than America's current losses, and our descent appears far trickier to navigate.

As we look to address our current fall from grace, lest we forget, the United States faced two major declines of its power during the cold war as well. Neither was without risk. The first occurred shortly after World War II, when the devastation of the Soviet, European and many Asian economies, combined with the increasingly productive American economy, left the United States with a far larger share of gross world product-41 percent in 1948-than it even possessed in the age of unipolar dominance beginning in 1991. As the war-torn economies recovered, U.S. share of world product fell 20 percent by 1961 while that of its main rival, the Soviet Union, grew by 167 percent. This relative American decline corresponds to the height of U.S.-Soviet cold-war rivalry in Europe and Asia. Eight of the nine U.S.-Soviet nuclear crises occurred from 1948-1962, all of which involved efforts by the Soviet Union or its allies to revise the political status quo in their favor⁷-that is, all could be reasonably interpreted as instances in which the United States or its allies became the targets of opportunistic aggression.

The second major U.S. relative decline occurred from 1970 to 1980, when the U.S. share of world product fell 27 percent. This decade brought with it challenges to America's position in the world. This was especially true toward the end of the decade with the Soviet invasion of Afghanistan and the Iranian Revolution, which collectively increased concern about Soviet dominance of Persian Gulf oil. However, the 1970s was mainly a period of "détente" between the cold-war protagonists, which corresponds to the fact that the shares of world product for both the United States and the Soviet Union were in decline. In other words, it is reasonable to think that America's decline in the 1970s did not lead to more significant trouble for the United States because its main rival was descending even faster.

Clearly, major shifts in the balance of power in the international system often lead to instability and conflict. And America's current predicament is far more severe. This time, our relative decline of 32 percent is accompanied, not by an even-steeper decline of our near-peer competitor, but rather by a 144 percent increase in China's relative position. Further, the rapid spread of technology and technological breakthroughs means that one great discovery does not buoy an already-strong state to decades-long predominance. And with a rising China-with raw resources of population, landmass and increasing adoption of leading technology-a true peer competitor is looming. America's current, rapid domestic economic decline is merely accelerating our own downfall.

The distinct quality of a system with only one superpower is that no other single state is powerful enough to balance against it. A true global hegemon is more powerful still-stronger than all second-ranked powers acting as members of a counterbalancing coalition seeking to contain the unipolar leader. By these standards, America's relative decline is fundamentally changing international politics, and is fundamentally different from Russia circa 1850 and Great Britain circa 1910.

In current-U.S.-dollar terms-the preferred measure of the unipolar-dominance school-the United States has already fallen far from being a global hegemon and unipolarity itself is waning, since China will soon have as much economic potential to balance the United States as did the Soviet Union during the cold war.

At the beginning of the 1990s, the United States was indeed not only stronger than any other state individually, but its power relative to even the collective power of all other major states combined grew from 1990 to 2000. Although the growth was small, America almost reached the crucial threshold of 50 percent of major-power product necessary to become a true global hegemon. So it is understandable that we were lulled into a sense of security, believing we could do as we wished, whenever and wherever we wished. The instability and danger of the cold war quickly became a distant memory.

Near the time of the Iraq War, it would have required virtually every major power to actively oppose the United States in order to assemble a counterbalancing coalition that could approximate America's potential power. Under the circumstances, hard, military balancing against the United States was not a serious possibility. So, it is not surprising that major powers opted for soft-balancing measures-relying on institutional, economic and diplomatic tools to oppose American military power. And yet we are beginning to see "the conflict of history" repeat itself.

Even with less relative power, in the run-up to the Iraq War, people grossly underrated the ability of Germany, France, Russia and China, along with important regional powers like Turkey, to soft balance against the United States; for instance, to use the United Nations to delay, complicate and ultimately deny the use of one-third of U.S. combat power (the Fourth Infantry Division) in the opening months of the Iraq War. This is not yet great-power war of the kind seen in centuries past, but it harkens the instability that future unilateral efforts may trigger.

The balance of world power circa 2008 and 2013 shows a disturbing trend. True, the United States remains stronger than any other state individually, but its power to stand up to the collective opposition of other major powers is falling precipitously. Though these worlds depict potential power, not active counterbalancing coalitions, and this type of alliance may never form, nonetheless, American relative power is declining to the point where even subsets of major powers acting in concert could produce sufficient military power to stand a reasonable chance of successfully opposing American military policies.

Indeed, if present trends continue to 2013 and beyond, China and Russia, along with any one of the other major powers, would have sufficient economic capacity to mount military opposition at least as serious as did the Soviet Union during the cold war. And it is worth remembering that the Soviet Union never had more than about half the world product of the United States, which China alone is likely to reach in the coming decade. The faults in the arguments of the unipolar-dominance school are being brought into sharp relief. The world is slowly coming into balance. Whether or not this will be another period of great-power transition coupled with an increasing risk of war will largely depend on how America can navigate its decline. Policy makers must act responsibly in this new era or risk international opposition that poses far greater costs and far greater dangers.

A COHERENT grand strategy seeks to balance a state's economic resources and its foreign-policy commitments and to sustain that balance over time. For America, a coherent grand strategy also calls for rectifying the current imbalance between our means and our ends, adopting policies that enhance the former and modify the latter.

Clearly, the United States is not the first great power to suffer long-term decline-we should learn from history. Great powers in decline seem to almost instinctively spend more on military forces in order to shore up their disintegrating strategic positions, and some like Germany go even further, shoring up their security by adopting preventive military strategies, beyond defensive alliances, to actively stop a rising competitor from becoming dominant.

For declining great powers, the allure of preventive war-or lesser measures to "merely" firmly contain a rising power-has a more compelling logic than many might assume. Since Thucydides, scholars of international politics have famously argued that a declining hegemon and rising challenger must necessarily face such intense security competition that hegemonic war to retain dominance over the international system is almost a foregone conclusion. Robert Gilpin, one of the deans of realism who taught for decades at Princeton, believed that "the first and most attractive response to a society's decline is to eliminate the source of the problem . . . [by] what we shall call a hegemonic war."

Yet, waging war just to keep another state down has turned out to be one of the great losing strategies in history. The Napoleonic Wars, the Austro-Prussian War, the Franco-Prussian War, German aggression in World War I, and German and Japanese aggression in World War II were all driven by declining powers seeking to use war to improve their future security. All lost control of events they thought they could control. All suffered ugly defeats. All were worse-off than had they not attacked.

As China rises, America must avoid this great-power trap. It would be easy to think that greater American military efforts could offset the consequences of China's increasing power and possibly even lead to the formation of a multilateral strategy to contain China in the future. Indeed, when China's economic star began to rise in the 1990s, numerous voices called for precisely this, noting that on current trajectories China would overtake the United States as the world's leading economic power by 2050.⁸ Now, as that date draws nearer-indeed, current-dollar calculations put the crossover point closer to 2040-and with Beijing evermore dependent on imported oil for continued economic growth, one might think the case for actively containing China is all the stronger.

Absent provocative military adventures by Beijing, however, U.S. military efforts to contain the rising power are most likely doomed to failure. China's growth turns mainly on domestic issues-such as shifting the workforce from rural to urban areas-that are beyond the ability of outside powers to significantly influence. Although China's growth also depends on external sources of oil, there is no way to exploit this vulnerability short of obviously hostile alliances (with India, Indonesia, Taiwan and Japan) and clearly aggressive military measures (controlling the sea-lanes from the Persian Gulf to Asia) that together could deny oil to China. Any efforts along these lines would likely backfire-and only exacerbate America's problems, increasing the risk of counterbalancing.

Even more insidious is the risk of overstretch. This self-reinforcing spiral escalates current spending to maintain increasingly costly military commitments, crowding out productive investment for future growth.

Today, the cold-war framework of significant troop deployments to Europe, Asia and the Persian Gulf is coming unglued. We cannot afford to keep our previous promises. With American forces bogged down in Iraq and Afghanistan and mounting troubles in Iran and Pakistan, the United States has all but gutted its military commitments to Europe, reducing our troop levels far below the one hundred thousand of the 1990s. Nearly half have been shifted to Iraq and elsewhere. Little wonder that Russia found an opportunity to demonstrate the hollowness of the Bush administration's plan for expanding NATO to Russia's borders by scoring a quick and decisive military victory over Georgia that America was helpless to prevent. If a large-scale conventional war between China and Taiwan broke out in the near future, one must wonder whether America would significantly shift air and naval power away from its ongoing wars in the Middle East in order to live up to its global commitments. If the United States could not readily manage wars in Iraq and Afghanistan at the same time, could it really wage a protracted struggle in Asia as well? And as the gap between America's productive resources and global commitments grows, why will others pass up opportunities to take advantage of America's overstretched grand strategy?

Since the end of the cold war, American leaders have consistently claimed the ability to maintain a significant forward-leaning military presence in the three major regions of the globe and, if necessary, to wage two major regional wars at the same time. The harsh reality is that the United States no longer has the economic capacity for such an ambitious grand strategy. With 30 percent of the world's product, the United States could imagine maintaining this hope. Nearing 20 percent, it cannot.

Yet, just withdrawing American troops from Iraq is not enough to put America's grand strategy into balance. Even assuming a fairly quick and problem-free drawdown, the risks of instability in Iraq, Afghanistan and elsewhere in the region are likely to remain for many years to come. Further, even under the most optimistic scenarios, America is likely to remain dependent on imported oil for decades. Together, these factors point toward the Persian Gulf remaining the most important region in American grand strategy.

So, as Europe and Asia continue to be low-order priorities, Washington must think creatively and look for opportunities to make strategic trades. America needs to share the burden of regional security with its allies and continue to draw down our troop levels in Europe and Asia, even considering the attendant risks. The days when the United States could effectively solve the security problems of its allies in these regions almost on its own are coming to an end. True, spreading defense burdens more equally will not be easy and will be fraught with its own costs and risks. However, this is simply part of the price of America's declining relative power.

The key principle is for America to gain international support among regional powers like Russia and China for its vital national-security objectives by adjusting less important U.S. policies. For instance, Russia may well do more to discourage Iran's nuclear program in return for less U.S. pressure to expand NATO to its borders.

And of course America needs to develop a plan to reinvigorate the competitiveness of its economy. Recently, Harvard's Michael Porter issued an economic blueprint to renew America's environment for innovation. The heart of his plan is to remove the obstacles to increasing investment in science and technology. A combination of targeted tax, fiscal and education policies to stimulate more productive investment over the long haul is a sensible domestic component to America's new grand strategy. But it would be misguided to assume that the United States could easily regain its previously dominant economic position, since the world will likely remain globally competitive.

To justify postponing this restructuring of its grand strategy, America would need a firm expectation of high rates of economic growth over the next several years. There is no sign of such a burst on the horizon. Misguided efforts to extract more security from a declining economic base only divert potential resources from investment in the economy, trapping the state in an ever-worsening strategic dilemma. This approach has done little for great powers in the past, and America will likely be no exception when it comes to the inevitable costs of desperate policy making.

The United States is not just declining. Unipolarity is becoming obsolete, other states are rising to counter American power and the United States is losing much of its strategic freedom. Washington must adopt more realistic foreign commitments.

SINCE 2000, a systemic change has been occurring in the economic foundations of America's relative power, and it may fall even further in the foreseeable future. None of the dramatic consequences for U.S. grand strategy is likely to be immediate, but neither are those effects easily avoidable. For nearly two decades, the United States has experienced tremendous latitude in how it chooses to conduct itself in the world. But that latitude is now shrinking, and American policy makers must face facts. With the right grand strategy, however, America can mitigate the consequences of its relative decline, and possibly even reverse it.

Robert A. Pape is a professor of political science at the University of Chicago.

The author would like to thank Felicity Bloom, Daragh Grant, Jacob Homan, Chaim Kaufmann, Nuno Monteiro and especially Ken Feldman.

¹ For excellent discussions of the concept of power, see John Mearsheimer, The Tragedy of Great Power Politics (New York: W. W. Norton, 2001), ch. 3; and Edward Vose Gulick, Europe's Classical Balance of Power (New York: W. W. Norton, 1955), ch 1.

² Stephen G. Brooks and William C. Wohlforth, World Out of Balance: International Relations and the Challenge of American Primacy (Princeton, NJ: Princeton University Press, 2008), 32.

³ For explanations of different measures of gross domestic product, see glossaries for the International Monetary Fund, "World Economic Outlook Database" (October 2008) and World Bank, "World Development Indicators" (2008), both available online.

⁴ For a classic study of the diffusion of technology in past eras, see David S. Landes, The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to Present (New York: Cambridge University Press, 1969).        
⁵ See the Global Market Information Database; CIA World Factbook for the above dates; the National Science Board's "Science and Engineering Indicators 2008"; Nationmaster.com; and International Telecommunication Union's "International Communication Statistics, 2007." All were accessed online from August to October 2008.

⁶ This counterfactual calculation and the one in the next paragraph rely on the current-dollar method preferred by the unipolar-dominance school.

⁷ Richard K. Betts, Nuclear Blackmail and Nuclear Balance (Washington, DC: Brookings Institution Press, 1987).

⁸ For instance, Richard Bernstein and Ross H. Munro, The Coming Conflict with China (New York: Alfred A. Knopf, 1997).