pre_text: .
post_text: the black-scholes option valuation model was developed for use in estimating the fair value of traded options which have no vesting restrictions and are fully transferable . in addition , option valuation models require the input of highly subjective assumptions , including the expected stock price volatility . because the company 2019s employee stock options have characteristics significantly different from those of traded options , and because changes in the subjective input assumptions can materially affect the fair value estimate , in management 2019s opinion , the existing models do not necessarily provide a reliable single measure of the fair value of its employee stock options . the fair value of the rsus was determined based on the market value at the date of grant . the total fair value of awards vested during 2008 , 2007 , and 2006 was $ 35384 , $ 17840 , and $ 9413 , respectively . the total stock based compensation expense calculated using the black-scholes option valuation model in 2008 , 2007 , and 2006 was $ 38872 , $ 22164 , and $ 11913 , respectively.the aggregate intrinsic values of options outstanding and exercisable at december 27 , 2008 were $ 8.2 million and $ 8.2 million , respectively . the aggregate intrinsic value of options exercised during the year ended december 27 , 2008 was $ 0.6 million . aggregate intrinsic value represents the positive difference between the company 2019s closing stock price on the last trading day of the fiscal period , which was $ 19.39 on december 27 , 2008 , and the exercise price multiplied by the number of options exercised . as of december 27 , 2008 , there was $ 141.7 million of total unrecognized compensation cost related to unvested share-based compensation awards granted to employees under the stock compensation plans . that cost is expected to be recognized over a period of five years . employee stock purchase plan the shareholders also adopted an employee stock purchase plan ( espp ) . up to 2000000 shares of common stock have been reserved for the espp . shares will be offered to employees at a price equal to the lesser of 85% ( 85 % ) of the fair market value of the stock on the date of purchase or 85% ( 85 % ) of the fair market value on the enrollment date . the espp is intended to qualify as an 201cemployee stock purchase plan 201d under section 423 of the internal revenue code . during 2008 , 2007 , and 2006 , 362902 , 120230 , and 124693 shares , respectively were purchased under the plan for a total purchase price of $ 8782 , $ 5730 , and $ 3569 , respectively . at december 27 , 2008 , approximately 663679 shares were available for future issuance . 10 . earnings per share the following table sets forth the computation of basic and diluted net income per share: .
table: 2008 2007 2006
table: Weighted average fair value of options granted $18.47 $33.81 $20.01
table: Expected volatility 0.3845 0.3677 0.3534
table: Dividend yield 3.75% 0.76% 1.00%
table: Expected life of options in years 6.0 6.0 6.3
table: Risk-free interest rate 2% 4% 5%
question: Analyse this data from a financial earnings document. what was the estimated percentual increase in the expected volatility observed during 2007 and 2008?