american tower corporation and subsidiaries notes to consolidated financial statements as of december 31 , 2010 , total unrecognized compensation expense related to unvested restricted stock units granted under the 2007 plan was $ 57.5 million and is expected to be recognized over a weighted average period of approximately two years .
employee stock purchase plan 2014the company maintains an employee stock purchase plan ( 201cespp 201d ) for all eligible employees .
under the espp , shares of the company 2019s common stock may be purchased during bi-annual offering periods at 85% ( 85 % ) of the lower of the fair market value on the first or the last day of each offering period .
employees may purchase shares having a value not exceeding 15% ( 15 % ) of their gross compensation during an offering period and may not purchase more than $ 25000 worth of stock in a calendar year ( based on market values at the beginning of each offering period ) .
the offering periods run from june 1 through november 30 and from december 1 through may 31 of each year .
during the 2010 , 2009 and 2008 offering periods employees purchased 75354 , 77509 and 55764 shares , respectively , at weighted average prices per share of $ 34.16 , $ 23.91 and $ 30.08 , respectively .
the fair value of the espp offerings is estimated on the offering period commencement date using a black-scholes pricing model with the expense recognized over the expected life , which is the six month offering period over which employees accumulate payroll deductions to purchase the company 2019s common stock .
the weighted average fair value for the espp shares purchased during 2010 , 2009 and 2008 was $ 9.43 , $ 6.65 and $ 7.89 , respectively .
at december 31 , 2010 , 8.7 million shares remain reserved for future issuance under the plan .
key assumptions used to apply this pricing model for the years ended december 31 , are as follows: .

2010
2009
2008
Range of risk-free interest rate
0.22% - 0.23%
0.29% - 0.44%
1.99% - 3.28%
Weighted average risk-free interest rate
0.22%
0.38%
2.58%
Expected life of shares
6 months
6 months
6 months
Range of expected volatility of underlying stock price
35.26% - 35.27%
35.31% - 36.63%
27.85% - 28.51%
Weighted average expected volatility of underlying stock price
35.26%
35.83%
28.51%
Expected annual dividends
N/A
N/A
N/A

13 .
stockholders 2019 equity warrants 2014in august 2005 , the company completed its merger with spectrasite , inc .
and assumed outstanding warrants to purchase shares of spectrasite , inc .
common stock .
as of the merger completion date , each warrant was exercisable for two shares of spectrasite , inc .
common stock at an exercise price of $ 32 per warrant .
upon completion of the merger , each warrant to purchase shares of spectrasite , inc .
common stock automatically converted into a warrant to purchase shares of the company 2019s common stock , such that upon exercise of each warrant , the holder has a right to receive 3.575 shares of the company 2019s common stock in lieu of each share of spectrasite , inc .
common stock that would have been receivable under each assumed warrant prior to the merger .
upon completion of the company 2019s merger with spectrasite , inc. , these warrants were exercisable for approximately 6.8 million shares of common stock .
of these warrants , warrants to purchase approximately none and 1.7 million shares of common stock remained outstanding as of december 31 , 2010 and 2009 , respectively .
these warrants expired on february 10 , 2010 .
stock repurchase program 2014during the year ended december 31 , 2010 , the company repurchased an aggregate of approximately 9.3 million shares of its common stock for an aggregate of $ 420.8 million , including commissions and fees , of which $ 418.6 million was paid in cash prior to december 31 , 2010 and $ 2.2 million was included in accounts payable and accrued expenses in the accompanying consolidated balance sheet as of december 31 , 2010 , pursuant to its publicly announced stock repurchase program , as described below. .

Question: Analyse this data from a financial earnings document. what was the percentage change in the weighted average fair value for the espp shares purchased from 2009 to 2010
Choices:
-0.41805
0.09242
0.41805
2.39209
29.22556
Correct choice index: 2