The result is a more divided world than the leaders faced at previous summits of the Group of 20 - a disparity that could make any breakthroughs at the summit elusive.
Issues beyond economic ones will surely seize part of the agenda. The threat of a US-led military strike against Syria, in response to what the Obama Administration calls a deadly chemical weapons attack, is certain to arise. Russian President Vladimir Putin, an ally of Syrian President Bashar Assad and the host of the G20 summit, has asked President Barack Obama to reconsider any military action.
Europe's financial crisis, and fears that the euro currency alliance might unravel, brought focus to previous summits. The leaders first met in 2008 as the US financial crisis was infecting economies around the world.
"There is a stronger incentive to co-operate if you are on the brink of a crisis," said Domenico Lombardi, an economist at the Center for International Governance Innovation in Canada.
Without such a threat, "each country is looking after its own domestic affairs".
After their first meetings, for example, the G20 leaders embraced policies to try to rejuvenate the global economy. Last year, they agreed to boost the International Monetary Fund's financial resources, which had been depleted by Europe's crisis.
"The G-20 did pretty well in crisis-response mode," said Fred Bergsten, director emeritus at the Peterson Institute for International Economics. "The question now is whether it can transfer from being purely a crisis-response mechanism to a crisis-prevention mechanism."
The problems engulfing emerging countries like India, Indonesia and Turkey are a challenge. They stem in part from expectations that the Federal Reserve will soon slow its monthly bond purchases.
The bond purchases have been intended to keep US borrowing rates ultra-low to stimulate growth.
Long-term US rates have been rising in anticipation of the Fed slowing its bond buying. Those rates have led investors to pull money from developing countries and invest it in US assets.
India's currency, the rupee, Indonesia's rupiah and Brazil's real, among others, have plunged in response.
Yet the advanced countries aren't likely to alter their rate policies in response to the turmoil in emerging nations. Those policies have been vital to the recoveries in the United States, Europe and Japan.
But the leaders will probably address the developing countries' concerns in their statement when the summit ends.
Chinese deputy finance minister Zhu Guangyao said the United States "must consider the spillover effect" of scaling back its bond-buying.
China isn't as vulnerable to the Fed's policies as other developing countries. It limits its currency's ability to fluctuate, and it has sealed off its financial system from global capital flows.
India, Asia's third-largest economy, has been especially hard hit by the Fed's polices.
Its economy is hobbled by high fuel costs, low exports and poor infrastructure.
India has restricted the amount of money Indians can send out of the country and has boosted import taxes to try to stem the rupee's slide.
But double-digit inflation has forced India's central bank to boost interest rates, making borrowing costlier for consumers and businesses.
Growth slowed to an annual rate of 4.4 per cent in the April-June quarter, down from an average rate of 8 per cent from 2003 through 2011.
World Bank President Jim Yong Kim said this week that he was concerned about the Fed's impact on emerging economies. Kim noted, though, that some of those economies must address their own underlying weaknesses.
In advanced economies, rates remain low and growth steady.
European Central Bank president Mario Draghi helped shore up Europe's economy by declaring last year that he would do "whatever it takes" to save the euro currency.
The 17 nations that share the euro finally emerged from recession in the second quarter of the year after shrinking for six straight quarters.
Economic data since then suggests a modest recovery will endure. Consumer confidence is up. Manufacturing surveys point to higher output. Many European stock markets are up this year.
Likewise, in Japan, Prime Minister Shinzo Abe has increased government spending and pushed the Bank of Japan to step up bond purchases to try to jolt the economy out of two decades of stagnation.
Japan's economy expanded at a 2.6 per cent annual rate in the April-June quarter after growing at a 3.8 per cent rate in the first three months of the year.
The US economy has expanded steadily if modestly since its recession ended more than four years ago.
The Fed's low-rate policies are credited with spurring home and car purchases and creating jobs. The US economy grew at a 2.5 per cent annual rate in the second quarter, the Government says.
But consumer spending hasn't rebounded as much as in previous recoveries.
That weakness has deprived the global economy of one of its long-standing engines - the American shopper. The world economy now depends on multiple sources of growth.
"There is no single economy that dominates the global economy anymore or will solve global problems ... by getting its act together on its own," says Barry Eichengreen, an economics professor at the University of California, Berkeley.
- AP
