Considering 30-days investment horizon, Teck Resources Limited is expected to under-perform the BHP Billiton. In addition to that, Teck is 1.36 times more volatile than BHP Billiton Limited. It trades about -0.38 of its total potential returns per unit of risk. BHP Billiton Limited is currently generating about -0.25 per unit of volatility. If you would invest  6,917  in BHP Billiton Limited on May 20, 2013 and sell it today you would lose (657) from holding BHP Billiton Limited or give up 9.5% of portfolio value over 30 days.