CHEVRON CORP | 2013 | FY | 3

The fair market values of stock options and stock appreciation rights granted in 2013, 2012 and 2011 were measured on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions:
 
Year ended December 31
 
2013

 
 
2012

 
2011

 
Stock Options
 
 
 
 
 
 

Expected term in years1
6.0



6.0


6.2


Volatility2
31.3

%

31.7

%
31.0

%
Risk-free interest rate based on zero coupon U.S. treasury note
1.2

%

1.1

%
2.6

%
Dividend yield
3.3

%

3.2

%
3.6

%
Weighted-average fair value per option granted
$
24.48



$
23.35


$
21.24


1 
Expected term is based on historical exercise and postvesting cancellation data.
2 
Volatility rate is based on historical stock prices over an appropriate period, generally equal to the expected term.

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