As Fed, China pull back, so do global markets Fresh evidence that the Chinese economy is slowing triggered a sell-off in global stock markets that capped the worst weekly losses on Wall Street in more than a year. The Dow Jones industrial average and the S&P 500-stock index each declined about 2 percent Friday, with weekly losses of about 3.5 percent and 2.5 percent, respectively. Markets in Europe and Asia suffered similar declines after a measure of Chinese manufacturing activity fell. Across a number of developing countries, meanwhile, the adjustment to the slowdown of Federal Reserve monetary stimulus began to accelerate, as traders dumped local currency in Turkey, South Africa and elsewhere - a rout that touched off concerns of a new crisis brewing in one or more of the world's once-vibrant emerging markets. The sell-off in the markets, which are down since the start of 2014, follows a dramatic run-up that many analysts said was unlikely to continue, even with the U.S. economy gaining steam. However, the confluence of events behind it emphasized the tight linkages in the global economy and the uncertain effect that the Federal Reserve's tapering will have over time. China has become a major prop of world economic growth, and a slowdown there will show up on the books of virtually every major trading nation and company - affecting orders for metal ores from Indonesia and Brazil, heavy equipment from the United States and Germany, and the flow of money to African nations where China has become a major investor. Compounding the trouble is a growing fear that China's massive investment in building and infrastructure in recent years - part of its effort to stoke growth during the 2008 financial crisis - will show up in unsustainable levels of debt and bad loans for local governments and banks. Officials and analysts downplay the likelihood that China's troubles will touch off global problems akin to those caused by the U.S. financial system. The country's capital markets and banks are not as closely interwoven with the rest of the world, and the Chinese government has stashed away trillions of dollars in foreign reserves to use as a buffer. But there is still a fear that the country - the world's second-largest economy - is facing major financial and demographic constraints that could limit its growth and force a major correction to its banking sector. Authorities there "are aware of that," World Bank chief economist Kaushik Basu said in a recent interview with reporters. "The bad news is that there is no science for this," and efforts to limit credit and investment in the country could slow its economy even further. The impact of Federal Reserve policy is another unknown. Analysts at the International Monetary Fund, for example, have been generally sanguine about how the Fed's slowdown in bond buying will affect the world. There was a brief "taper panic" in mid-2013, when the Fed appeared ready to start its drawdown - a moment that marked, in a sense, the formal end of the U.S. crisis response. After that, many analysts said that a gradual end of Fed asset purchases would be offset by a strengthening U.S. economy, because the Fed would not reduce its monetary stimulus otherwise. But the impact may still be serious in some nations, notably those that rely on foreign currency to finance trade and other deficits. The tremors started showing up this week as currencies in Turkey, South Africa and elsewhere plunged. There may be less likelihood that problems in one of those places turns into a global disease, as happened in the 1990s in Latin America and Asia. Still, "we're seeing a gradual and cumulative realization that the growth prospects for many [emerging market] economies, long seen as a given, are in fact problematic," Patrick Chovanec, managing director of Silvercrest Asset Management, said in a research note.