mastercard incorporated notes to consolidated financial statements 2014 ( continued ) ( in thousands , except percent and per share data ) upon termination of employment , excluding retirement , all of a participant 2019s unvested awards are forfeited . however , when a participant terminates employment due to retirement , the participant generally retains all of their awards without providing additional service to the company . eligible retirement is dependent upon age and years of service , as follows : age 55 with ten years of service , age 60 with five years of service and age 65 with two years of service . compensation expense is recognized over the shorter of the vesting periods stated in the ltip , or the date the individual becomes eligible to retire . there are 11550 shares of class a common stock reserved for equity awards under the ltip . although the ltip permits the issuance of shares of class b common stock , no such shares have been reserved for issuance . shares issued as a result of option exercises and the conversions of rsus are expected to be funded with the issuance of new shares of class a common stock . stock options the fair value of each option is estimated on the date of grant using a black-scholes option pricing model . the following table presents the weighted-average assumptions used in the valuation and the resulting weighted- average fair value per option granted for the years ended december 31: .

2009: risk-free rate of return: -2.5
expected term ( in years ): 6.17
expected volatility: -41.7
expected dividend yield: -0.4
weighted-average fair value per option granted: 71.03
2008: risk-free rate of return: -3.2
expected term ( in years ): 6.25
expected volatility: -37.9
expected dividend yield: -0.3
weighted-average fair value per option granted: 78.54
2007: risk-free rate of return: -4.4
expected term ( in years ): 6.25
expected volatility: -30.9
expected dividend yield: -0.6
weighted-average fair value per option granted: 41.03

the risk-free rate of return was based on the u.s . treasury yield curve in effect on the date of grant . the company utilizes the simplified method for calculating the expected term of the option based on the vesting terms and the contractual life of the option . the expected volatility for options granted during 2009 was based on the average of the implied volatility of mastercard and a blend of the historical volatility of mastercard and the historical volatility of a group of companies that management believes is generally comparable to mastercard . the expected volatility for options granted during 2008 was based on the average of the implied volatility of mastercard and the historical volatility of a group of companies that management believes is generally comparable to mastercard . as the company did not have sufficient publicly traded stock data historically , the expected volatility for options granted during 2007 was primarily based on the average of the historical and implied volatility of a group of companies that management believed was generally comparable to mastercard . the expected dividend yields were based on the company 2019s expected annual dividend rate on the date of grant. .

Questions:
what is the risk-free rate in 2009?
what about in 2008?
what is the net change?
what percentage change does this represent?
what is the net change in weighted-average fair value per option granted from 2007 to 2008?
what is the weighted-average fair value per option granted	in 2007?
what growth rate does this represent?

Answers:
2.5
3.2
0.7
21.9%
37.51
41.03
91.4%