notes to the audited consolidated financial statements for 2007 , 2006 , and 2005 , total share-based compensation expense ( before tax ) of approximately $ 26 million , $ 29 million , and $ 22 million , respectively , was recognized in selling , general and administrative expense in the consolidated statement of earnings for all share-based awards of which approximately $ 13 million , $ 17 million , and $ 5 million , respectively , related to stock options . sfas no . 123 ( r ) requires that compensation expense is recognized over the substantive vesting period , which may be a shorter time period than the stated vesting period for retirement-eligible employees . for 2007 and 2006 , approximately $ 3 million and $ 8 million , respectively , of stock option compensation expense were recognized due to retirement eligibility preceding the requisite vesting period . stock option awards option awards are granted on an annual basis to non-employee directors and to employees who meet certain eligibility requirements . option awards have an exercise price equal to the closing price of the company's stock on the date of grant . the term life of options is ten years with vesting periods that vary up to three years . vesting usually occurs ratably over the vesting period or at the end of the vesting period . the company utilizes the black scholes merton ( "bsm" ) option valuation model which relies on certain assumptions to estimate an option's fair value . the weighted average assumptions used in the determination of fair value for stock options awarded in 2007 , 2006 , and 2005 are provided in the table below: .

Table:
assumptions | 2007 | 2006 | 2005
expected volatility rate | 20.80% ( 20.80 % ) | 21.40% ( 21.40 % ) | 22.90% ( 22.90 % )
expected dividend yield | 2.92% ( 2.92 % ) | 3.24% ( 3.24 % ) | 3.29% ( 3.29 % )
average risk-free interest rate | 4.24% ( 4.24 % ) | 4.62% ( 4.62 % ) | 4.48% ( 4.48 % )
expected forfeiture rate | 0.75% ( 0.75 % ) | 0.75% ( 0.75 % ) | actual
expected term years | 4.40 | 4.40 | 5.00
the volatility rate of grants is derived from historical company common stock price volatility over the same time period as the expected term of each stock option award .
the volatility rate is derived by mathematical formula utilizing the weekly high closing stock price data over the expected term .
the expected dividend yield is calculated using the expected company annual dividend amount over the expected term divided by the fair market value of the company's common stock .
the average risk-free interest rate is derived from united states department of treasury published interest rates of daily yield curves for the same time period as the expected term .
sfas no .
123 ( r ) specifies only share-based awards expected to vest be included in share-based compensation expense .
estimated forfeiture rates are determined using historical forfeiture experience for each type of award and are excluded from the quantity of awards included in share-based compensation expense .
the weighted average expected term reflects the analysis of historical share-based award transactions and includes option swap and reload grants which may have much shorter remaining expected terms than new option grants. .

Question: what was the average expected volatility rate from 2005 to 2007
Answer: 21.7%
Calculation: add(20.80, 21.40), add(#0, 22.90), add(#1, const_3), divide(#2, const_2)