.
[['', '2008', '2007', '2006'], ['weighted average fair value of options granted', '$ 18.47', '$ 33.81', '$ 20.01'], ['expected volatility', '0.3845', '0.3677', '0.3534'], ['dividend yield', '3.75% ( 3.75 % )', '0.76% ( 0.76 % )', '1.00% ( 1.00 % )'], ['expected life of options in years', '6.0', '6.0', '6.3'], ['risk-free interest rate', '2% ( 2 % )', '4% ( 4 % )', '5% ( 5 % )']]
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: .

Question: what was the estimated percentual increase in the expected volatility observed during 2007 and 2008?
Answer: 4.5%
Explanation: it is the expected volatility in 2008 divided by the expected volatility in 2007 , then transformed into a percentage .