tax benefits recognized for stock-based compensation during the years ended december 31 , 2011 , 2010 and 2009 , were $ 16 million , $ 6 million and $ 5 million , respectively . the amount of northrop grumman shares issued before the spin-off to satisfy stock-based compensation awards are recorded by northrop grumman and , accordingly , are not reflected in hii 2019s consolidated financial statements . the company realized tax benefits during the year ended december 31 , 2011 , of $ 2 million from the exercise of stock options and $ 10 million from the issuance of stock in settlement of rpsrs and rsrs . unrecognized compensation expense at december 31 , 2011 there was $ 1 million of unrecognized compensation expense related to unvested stock option awards , which will be recognized over a weighted average period of 1.1 years . in addition , at december 31 , 2011 , there was $ 19 million of unrecognized compensation expense associated with the 2011 rsrs , which will be recognized over a period of 2.2 years ; $ 10 million of unrecognized compensation expense associated with the rpsrs converted as part of the spin-off , which will be recognized over a weighted average period of one year ; and $ 18 million of unrecognized compensation expense associated with the 2011 rpsrs which will be recognized over a period of 2.0 years . stock options the compensation expense for the outstanding converted stock options was determined at the time of grant by northrop grumman . there were no additional options granted during the year ended december 31 , 2011 . the fair value of the stock option awards is expensed on a straight-line basis over the vesting period of the options . the fair value of each of the stock option award was estimated on the date of grant using a black-scholes option pricing model based on the following assumptions : dividend yield 2014the dividend yield was based on northrop grumman 2019s historical dividend yield level . volatility 2014expected volatility was based on the average of the implied volatility from traded options and the historical volatility of northrop grumman 2019s stock . risk-free interest rate 2014the risk-free rate for periods within the contractual life of the stock option award was based on the yield curve of a zero-coupon u.s . treasury bond on the date the award was granted with a maturity equal to the expected term of the award . expected term 2014the expected term of awards granted was derived from historical experience and represents the period of time that awards granted are expected to be outstanding . a stratification of expected terms based on employee populations ( executive and non-executive ) was considered in the analysis . the following significant weighted-average assumptions were used to value stock options granted during the years ended december 31 , 2010 and 2009: .

2010: dividend yield: -2.9
volatility rate: -25
risk-free interest rate: -2.3
expected option life ( years ): 6
2009: dividend yield: -3.6
volatility rate: -25
risk-free interest rate: -1.7
expected option life ( years ): 5

the weighted-average grant date fair value of stock options granted during the years ended december 31 , 2010 and 2009 , was $ 11 and $ 7 , per share , respectively. .

Questions:
what was the dividend yield for 2010?
and for 2009?
so what was the difference between these two values?
and the value for 2009 again?
so what was the percentage decline during this time?

Answers:
2.9
3.6
-0.7
3.6
-19.4%