[["", "2013", "2012", "2011"], ["expected volatility", "28.9% ( 28.9 % )", "27.8% ( 27.8 % )", "27.3% ( 27.3 % )"], ["risk-free interest rate", "0.7% ( 0.7 % )", "0.8% ( 0.8 % )", "1.7% ( 1.7 % )"], ["dividend yield", "3.2% ( 3.2 % )", "3.2% ( 3.2 % )", "2.7% ( 2.7 % )"], ["expected life ( in years )", "4.5", "4.5", "4.4"], ["contractual life ( in years )", "7.0", "7.0", "7.0"]]