One of the big questions of our time is whether the global economy is stable. The gains from “globalization” – more cross-border trade, investment, and technology transfers – are indisputable. Countless millions have escaped poverty in Asia and Europe. A recent study by the Institute for International Economics concluded that American living standards are roughly 10% higher as a result of globalization’s benefits (cheap imports, greater competition, new technologies). Globalization’s winners vastly outnumber its losers.

Unfortunately, that could change if the world economy turns out to be unstable – incapable of sustaining adequate growth or vulnerable to severe crises. For the moment, the dangers are abstract. In 2004, the global economy grew 4.7%, report economists at Goldman Sachs. Asia (excluding Japan) grew 8.2%, Latin America 5.6%, the United States 4.4%. Still, the specter of instability lingers.

Global economic integration – the merging of markets, the mutual dependencies of countries – has raced well ahead of either political integration or intellectual mastery. We simply don’t understand well how the global economy operates. Nor is it clear how countries with diverging interests and shared suspicions will cooperate in a crisis.

One obvious problem is oil. Even if the United States could end its 64% dependence on imports (a practical impossibility anytime soon), Europe would still import 80% of its needs and Japan 100%.

Any major shutdown of Persian Gulf exports could devastate the world economy. Global terrorism or a world pandemic would also pose threats. Countries might protect themselves from outsiders – imposing restrictions on travel and trade – in ways that destroy global commerce.

At present, the greatest peril may lie in huge global trade imbalances – and the financial pressures they create. The basic dilemma is that the world needs American trade deficits as an “engine” of growth, compensating for weak growth in Europe and Japan. But the same trade deficits may now be destabilizing because they send large numbers of dollars abroad. The danger: a dollar “crash” on foreign-exchange markets that spills over into the U.S. stock and bond markets, driving down those markets and triggering a global recession.

Look at the numbers. In 2004, the U.S. current account deficit reached an estimated $650 billion, or a record 5.6% of gross domestic product, or GDP. (The current account includes all trade, plus other international payments such as travel and tourism.) The mirror images of U.S. deficits are other countries’ surpluses. In 2004, Japan’s current account surplus was 3.7% of GDP, Germany’s 2.9% and China’s 2.3%, estimates Economy.com.

What’s the problem? Foreign exporters receive dollars for their U.S. shipments. If those dollars aren’t reinvested in American assets – say U.S. stocks, bonds, or Treasury securities – they’ll be sold on foreign exchange markets for other currencies: the euro, the yen, the pound. As dollar sales drive down its value, foreigners note that their existing U.S. stocks and bonds are worth less in their own currencies. So they may sell U.S. securities to limit losses. At the end of 2003, foreigners owned $1.5 trillion in U.S. stocks; widespread sales could trigger steep market declines.

The risk is an economic implosion. A sinking stock market could damage American consumer confidence and spending. Higher currencies for Europe and Japan could weaken their export competitiveness. Together, the United States, Europe and Japan are half the global economy. If they went into recession, other countries might follow. Economists are divided. Some fear the worst, because the world is flooded with dollars. Relax, say others. Asian central banks (their versions of the Federal Reserve) will buy surplus dollars, because they want to export to the United States and don’t want their currencies to rise against the dollar. Still other economists (including Alan Greenspan) believe that we’ll muddle through – that shifts in exchange rates and economic growth will slowly narrow today’s trade imbalances. So far, the evidence supports everyone.

Every economic system requires a political framework, but the framework for the global economy is creaky. Twenty years ago, the “world economy” consisted mainly of the United States and its Cold War allies. Economic, military, and foreign policy objectives overlapped. Now, the world economy includes China, India, and the former Soviet Union. Global interdependence has inspired some cooperation – the SARS outbreak and Asia’s 1997-98 financial crisis being examples. But the political foundation for cooperation has weakened. Our relations with old Cold War allies are strained, while relations with new trading partners – China especially – are ambiguous. Could we someday be at war with China over Taiwan?

The well-being of advanced nations presumes a smoothly operating global economy. We take this for granted without knowing whether it will always be true. We don’t ask hard questions because we fear what the answers might be.