THIS year has turned out to be a surprisingly good one for the world economy. Global output has probably risen by close to 5%, well above its trend rate and a lot faster than forecasters were expecting 12 months ago. Most of the dangers that frightened financial markets during the year have failed to materialise. China's economy has not suffered a hard landing. America's mid-year slowdown did not become a double-dip recession. Granted, the troubles of the euro area's peripheral economies have proved all too real. Yet the euro zone as a whole has grown at a decent rate for an ageing continent, thanks to oomph from Germany, the fastest-growing big rich economy in 2010.

The question now is whether 2011 will follow the same pattern. Many people seem to think so. Consumer and business confidence is rising in most parts of the world; global manufacturing is accelerating; and financial markets are buoyant. The MSCI index of global share prices has climbed by 20% since early July. Investors today are shrugging off news far more ominous than that which rattled them earlier this year, from the soaring debt yields in the euro zone's periphery to news of rising inflation in China.

Earlier this year investors were too pessimistic. Now their breezy confidence seems misplaced. To oversimplify a little, the performance of the world economy in 2011 depends on what happens in three places: the big emerging markets, the euro area and America. (Yes, Japan is still an economic heavyweight, but it is less likely to yield surprises.) These big three are heading in very different directions, with very different growth prospects and contradictory policy choices. Some of this divergence is inevitable: even to the casual observer, India's economy has always been rather different from America's. But new splits are opening up, especially in the rich world, and with them come ever more chances for friction.

On the rise, on the edge, on the never-never

Begin with the big emerging markets, by far the biggest contributors to global growth this year. From Shenzhen to São Paulo these economies have been on a tear. Spare capacity has been used up. Where it can, foreign capital is pouring in. Isolated worries about asset bubbles have been replaced by a fear of broader overheating. China is the prime example (see article) but by no means alone. With Brazilian shops packed with shoppers, inflation there has surged above 5% and imports in November were 44% higher than the previous year.

Cheap money is often the problem. Though the slump of 2009 is a distant memory, monetary conditions are still extraordinarily loose, thanks, in many places, to efforts to hold down currencies (again, China leads in this respect). This combination is unsustainable. To stop prices accelerating, most emerging economies will need tighter policies next year. If they do too much, their growth could slow sharply. If they do too little, they invite higher inflation and a bigger tightening later. Either way, the chances of a macroeconomic shock emanating from the emerging world are rising steeply.

The euro area is another obvious source of stress, this time financial as well as macroeconomic. In the short term growth will surely slow, if only because of government spending cuts. In core countries, notably Germany, this fiscal consolidation is voluntary, even masochistic. The embattled economies on the periphery, such as Ireland, Portugal and Greece, have less choice and a grim future. Empirical evidence suggests that countries in a currency union are unlikely to be able to improve their competitiveness quickly by screwing down wages and prices (see article). Worse, the financial consequences of a shift to a world where a euro-area country can go bust are only just becoming clear. Not only do too many euro-zone governments owe too much, but Europe's entire banking model, which is based on thorough integration across borders, may need revisiting (see article). These difficulties would tax the most enlightened policymakers. The euro zone's political leaders, alas, are a fractious and underwhelming lot. An even bigger mess seems all but certain in 2011.

Reach for the stretch pants, Barack

America's economy, too, will shift, but in a different direction. Unlike Europe's, America's macroeconomic policy mix has just moved decisively away from austerity. The tax-cut agreement reached on December 7th by Barack Obama and congressional Republicans was far bigger than expected. Not only did it extend George Bush's expiring tax breaks for two years, but it also added more than 2% of GDP in new breaks for 2011 (see article). When this is coupled with the continued bond-buying of the Federal Reserve, America is injecting itself with another dose of stimulus steroids just when Europe is checking into rehab and enduring cold turkey.

The result of this could be that American output grows by as much as 4% next year. That is nicely above trend and enough to reduce unemployment, although not quickly. But America's politicians are taking a risk, too. Even though their country's long-term budget outlook is famously dire, Mr Obama and the Republicans did not even try to find an agreement on medium-term fiscal consolidation this week. Various proposals to fix the deficit look set to gather dust (see article). Bondholders, who have been very forgiving of the printer of the world's chief reserve currency, greeted the tax deal by selling Treasuries. Some investors, no doubt, see faster growth on the way; but a growing number are worried about the size of America's fiscal hole. If those worries take hold, the United States could even see a bond-market bust in 2011.

How much does this parting of the ways matter? The divergence between the world's big three will compound the risks in each one. America's loose monetary policy and concerns about sovereign defaults in the euro zone will encourage capital to flow to emerging economies, making the latter's central banks reluctant to raise interest rates and dampen down inflation. Over the next five years emerging economies are expected to account for over 50% of global growth but only 13% of the increase in net global public debt. Rather than rebalancing, the world economy in the immediate future will skew even more between a debt-ridden West and thrifty East.

The West avoided depression in part because Europe and America worked together and shared a similar economic philosophy. Now both are obsessed with internal problems and have adopted wholly opposite strategies for dealing with them. That bodes ill for international co-operation. Policymakers in Brussels will hardly focus on another trade round when a euro member is about to go bust. And it bodes ill for financial markets, since neither Europe's sticking-plaster approach to the euro nor America's “jam today, God knows what tomorrow” tactic with the deficit are sustainable.

Of course, it does not have to be this way. Now they have splurged the cash, Mr Obama and Congress could move on to a medium-term plan to reduce the deficit. Europe's feuding leaders could hash out a deal to put the single currency and the zone's banking system on a sustainable footing. And the big emerging economies could allow their currencies to rise. But don't bet on it. A more divided world economy could make 2011 a year of damaging shocks.