2013 | 2012 | 2011 | |||||||||
Dividend yield(1) | 0.86 | % | 0.73 | % | 0.69 | % | |||||
Expected volatility(2) | 16.94 | % | 22.88 | % | 20.42 | % | |||||
Risk-free interest rate(3) | 0.10 | % | 0.10 | % | 0.15 | % | |||||
Expected life (in years)(4) | 0.5 | 0.5 | 0.5 | ||||||||
Weighted-average grant date fair value | $ | 10.08 | $ | 9.22 | $ | 7.21 | |||||
(1) | The dividend yield is calculated based on semi-annual dividends paid and the fair market value of the Company’s stock at the grant date. |
(2) | The expected volatility is based on the historical volatility of the Company’s daily stock market prices over the previous six month period. |
(3) | The risk-free interest rate is based on the Treasury constant maturity interest rate whose term is consistent with the expected term of ESPP options (i.e., 6 months). |
(4) | The expected life is based on the semi-annual purchase period. |