The fierce debate on immigration ignores a crucial reality -- what is happening to the United States is only one piece, although a big one, of a much larger global picture.

That hit me a couple of weeks ago when I was in Singapore. The Southeast Asian island nation has long been hailed as an economic model, the business capital for the entire region.

But it is an economy facing demographic peril. Its small population of 4 million is shrinking, thanks to a very low fertility rate. Prosperous Singaporean couples work hard, have fewer children and worry about how to take care of their aging parents. By 2050, Singapore will have a median age of over 52, one of the oldest in the world.

Singapore's answer is to import labor. A third of its workforce are migrants, from construction workers to maids. One out of seven households employs a domestic worker -- low-paid women mostly from neighboring Philippines and Indonesia.

Singapore tries to lure "talents'' -- highly skilled and affluent migrants -- to stay permanently. But the men hauling bricks and the maids washing laundry are in a separate class of temporary guest workers, with no chance to join Singaporean society. If a maid becomes pregnant, she is shipped out within seven days. Employers have to post bonds that must be paid should their servants break the rules and try to stay, putting them in the role of migrant police.

Problems of abuse of domestic workers, including physical and sexual violence and confinement, are serious enough to have prompted a report last December by Human Rights Watch.

Singapore's dependence on migrant labor and its guest-worker policy may be at the extreme end but it's very much on the global spectrum. Labor, like capital and goods before it, is part of a global market. The movement of people across borders in search of wages and work, most of it from developing countries to developed, is growing at a phenomenal pace.

The numbers are staggering. From 1980 to 2000, the number of migrants living in the developed world more than doubled from 48 million to 110 million. Migrants make up an average 12 percent of the workforce in high-income countries. About 4 million migrants cross borders illegally every year.

The demand for labor is driven in part by a demographic disaster -- the falling birth rates of developed countries. Almost all of those countries now have fertility rates that are well below 2.1, the level at which a population replaces itself. At the very low end are Hong Kong (0.94), Korea (1.22) and Singapore in Asia (1.24), along with much of Eastern Europe.

Low fertility means shrinking workforces and aging populations. Without migration, according to a recent study, Europe's population would have declined by 4.4 million from 1995 to 2000. Immigration accounted for 75 percent of U.S. population growth during the same period.

This movement of people cannot be stopped, certainly not by hundreds of miles of fences or even by tens of thousands of border guards. It is an issue that cries out for global cooperation, for common policies that cut across national boundaries. Already, we can benefit from looking at what has worked -- and not worked -- elsewhere.

A Global Commission on International Migration, formed in 2003 by the United Nations secretary-general, has taken an initial stab. Their report, issued last winter, supports the growth of guest-worker programs.

The Senate immigration bill now up for debate includes a provision for a guest-worker program. The bill is clearly preferable to the punitive and ineffective approach of the House version. But the Singapore experience -- and previous guest-worker programs like the German import of Turks -- should prompt second thoughts about going down this road.

One problem is that the guests don't leave. The United States has its own experience with this in the bracero program to import farmworkers, and more recently with the supposedly temporary H1-B visas used so extensively by the high-tech industry here in Silicon Valley.

Most troubling to me, these programs create an underclass of migrants who are never assimilated, as happened in Germany. It sets us on the Singapore road, encouraging inhumane policing mechanisms. And it is a gilded invitation to employers to depress the wages and incomes of American workers, and not just in the dirty jobs that are supposedly so hard to fill.

The United States has been rightfully proud of a tradition that treats all immigrants as citizens in the making. Rather than guest workers, isn't it more American to set realistic immigration quotas and enforce them fairly?

"The United States is the most powerful since the Roman Empire," stated Stephen Walt, the Belfer Professor of International Affairs and academic dean of the John F. Kennedy School, Harvard University, delivering the 2005 Robert G. Wesson Lecture in International Relations Theory and Practice, at the Freeman Spogli Institute on November 16, 2005. America's unmatched power is therefore of great interest and concern to leaders in most other parts of the world, from President Putin in Russia, to President Chirac in France, and President Musharraf in Pakistan. For Americans, however, the key issue is how others are now responding to U.S. power.

Speaking before an audience of Stanford faculty, students, and the broader community, Professor Walt examined three interwoven themes: why other states do not welcome U.S. power; what are the main strategies available to them for dealing with American power? and what should the United States do in response?

As an integral part of his analysis, Walt showed opinion polls demonstrating a striking gap between American views of U.S. primacy and other countries' perceptions of the current U.S. role. For example, although the 2002 Pew Global Attitudes Project found that 79 percent of U.S. citizens believe it is good that "American ideas and customs are spreading around the world," and 70 percent think that U.S. foreign policy takes the interests of other states into account either "a great deal" or "a fair amount," overwhelming majorities overseas say the United States considers the interest of others "not much" or "not at all." Similarly, a 2005 BBC survey of 21 countries found only five, India, the Philippines, Poland, South Africa, and South Korea, where a majority of people had "positive" attitudes toward the United States.

There are three major sources of anti-Americanism, Walt explained. First, our sheer power makes other nations nervous. Second, there is a perceived sense of hypocrisy between our words and our actions. The case of nuclear weapons provides a vivid example. We preach nonproliferation, yet accord new respect and policy cooperation with newly nuclear states, such as India. Third, how the United States behaves in the world-what we do-invites antipathy. This latter point is abundantly clear in global opinion polls: Even in regions where anti-Americanism seems most strident, nations and individuals report that they do not object to our values or to what we stand for but rather to what we do.

Other nations, Walt pointed out, can choose a strategy of accommodation to our power or a strategy of resistance. Commonly adopted strategies of accommodation include 'bandwagoning," or realigning foreign policies with U.S. wishes, such as Libya's abandonment of nuclear weapons; "regional balancing"-using U.S. power to balance regional threats; "bonding" to curry favor with the United States; and "penetration," a strategy aimed at infiltrating the American political system to influence foreign policy outcomes.

In contrast, countries that choose to resist American power pursue five strategies:

"balancing" our power, alone or in alliance with others; "asymmetric responses," such as terrorism, which try to exploit specific areas of U.S. vulnerability; "blackmail," like North Korea's efforts to extract concessions from its nuclear weapons program; "balking," or tacit non-cooperation; and "delegitimizing," or attempts to turn others against the legitimacy of our actions or policies.

In light of the growing antipathy to U.S. primacy in so many parts of the world, Walt proposed three major courses of action to produce a more favorable response to U.S. power. First, he urged that we reduce American's military footprint abroad-and especially our ground force deployments-and return to a more traditional policy of regional balancing in cooperation with other nations. This policy would make greater use of American air and naval power and limit American intervention to cases where vital U.S. interests are threatened. Second, we should work harder to defend our international legitimacy and rebuild the U.S. image abroad, through a sustained campaign of public diplomacy and by keeping key American institutions-such as higher education-available to foreign visitors. Third, he advocated a more nuanced approach to America's traditional support for Israel, one that balances our genuine support for Israel's existence with the urgent need to bring a lasting settlement to the Israeli-Palestinian conflict.

"The more the United States uses its power in an overwhelming and capricious manner," Professor Walt warned, "the more the rest of the world will resist us." Conversely, the more the United States recognizes and respects the interests of others, while using its power to defend its own interests, the more other nations will welcome U.S. power. "The task we face," he advised, "is to rebuild the trust, admiration, and legitimacy the United States once enjoyed, so the rest of the world can focus not on taming U.S. power but on reaping the benefits it can bring."