The share price ofiShares Barclays 20+ Year Treasury ETF ( TLT ) -- which mainly holds 25-year bonds -- tumbled 11.4% from its 52-week high from July 25. ProShares Short 20+ Year Treasury ETF ( TBF ), designed to move opposite TLT, rises along with interest rates. The market faces "an impending rise in interest rates" as the economy improves and inflation heats up in 2014, says Jason Schenker, president of Austin-based Prestige Economics.