the fair value for these options was estimated at the date of grant using a black-scholes option pricing model with the following weighted-average assumptions for 2006 , 2005 and 2004: .

2006: weighted average fair value of options granted: 20.01
expected volatility: 0.3534
distribution yield: -1
expected life of options in years: 6.3
risk-free interest rate: -5
2005: weighted average fair value of options granted: 9.48
expected volatility: 0.3224
distribution yield: -0.98
expected life of options in years: 6.3
risk-free interest rate: -4
2004: weighted average fair value of options granted: 7.28
expected volatility: 0.3577
distribution yield: -1.3
expected life of options in years: 6.3
risk-free interest rate: -4

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 total fair value of shares vested during 2006 , 2005 , and 2004 was $ 9413 , $ 8249 , and $ 6418 respectively . the aggregate intrinsic values of options outstanding and exercisable at december 30 , 2006 were $ 204.1 million and $ 100.2 million , respectively . the aggregate intrinsic value of options exercised during the year ended december 30 , 2006 was $ 42.8 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 $ 55.66 on december 29 , 2006 , and the exercise price multiplied by the number of options outstanding . as of december 30 , 2006 , there was $ 64.2 million of total unrecognized compensation cost related to unvested share-based compensation awards granted to employees under the option 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 2006 , 2005 , and 2004 , 124693 , 112798 , and 117900 shares were purchased under the plan for a total purchase price of $ 3569 , $ 2824 , and $ 2691 , respectively . at december 30 , 2006 , approximately 1116811 shares were available for future issuance. .

Questions:
what was the number of shares that vested in 2006?
and what was that in 2005?
what was, then, the change over the year in the number of shares that vested?

Answers:
470
870
400