The downturn in prices is reflected in broad measures of commodity prices. The Standard & Poor's GSCI, an index tracking prices for crude oil, gold, copper and several other commodities, has dropped more than 6 percent this month so far. Even the price of gold, which usually rises when investors have concerns about the economy, has fallen. "This has been particularly perplexing to people in the gold market, because typically you think of gold as a safe haven," said David Greely, Goldman Sachs's head of energy research in New York. The drop in prices comes against a long backdrop of rising commodity prices, fed by the rapid development of such emerging economies as China and India, which have required more natural resources to fuel their growth. The increased demand drove up prices dramatically over the past decade. "China is really the intellectual underpinning of the commodities bubble - the idea they were going to buy everything in sight," said Gary Shilling, president of A. Gary Shilling & Co., an economic consulting firm. But Shilling and some others think that China's growth could be slowing, causing commodity prices to continue falling. The country is trying to shift its economy toward consumption rather than relying so heavily on exports. That dependence has made the country vulnerable recently, as demand has slowed in the United States and Europe. But there are wrinkles in the Chinese government's plans. A recent report showed that retail sales have been somewhat disappointing. Industrial production growth also slowed in April. And both imports and exports fell far short of expectations in April. Shilling thinks that despite all the concerns about inflation, it is in fact deflation that should worry policymakers because of its potential to significantly dampen economic growth. But after keeping short-term interest rates near zero, the Federal Reserve is short on tools for battling deflation, Shilling said. Even with its low-rate policy, the central bank has struggled to get banks to pump money into the economy, which would combat deflation. "They've tried about everything," said Shilling. What else can they do? . . . They really don't have much in the way of fire-power. Fears about what might happen if Greece exits the European Union also helped drive stocks to fall Monday. The Dow fell more than 125 points, or about 1 percent, while the S&P 500, a broader measure of stocks, dropped more than 1 percent. The euro, meanwhile, fell to less than $1.29. Greely cautioned that the dip in commodities prices was not a historic change that would undo the past several years of rising values. "A lot of what we're seeing now is a little more akin to what we saw in the fall when these European concerns came to the forefront," said Greely. And it's just led people to be very concerned about the state of the economy.