The iShares S&P GSCI Commodity Index Trust (NYSEArca: GSG), which tracks a basket of 24 different commodities, is down 14.55 percent year-to-date. SAN DIEGO (ETFguide.com) - Wall Street's ever rosy forecasts for accelerating economic growth aren't coming true. The Federal Reserve also knows that if inflation doesn't rise adequately enough, it could leave them without a valuable tool should the U.S. economy head into a double-dip scenario; the power to ease interest rates.