republic services , inc .
notes to consolidated financial statements 2014 ( continued ) 11 .
employee benefit plans stock-based compensation in february 2007 , our board of directors approved the 2007 stock incentive plan ( 2007 plan ) , and in may 2007 our shareholders ratified the 2007 plan .
in march 2011 , our board of directors approved the amended and restated 2007 stock incentive plan , and in may 2011 our shareholders ratified the amended and restated 2007 stock incentive plan .
in march 2013 , our board of directors approved the republic services , inc .
amended and restated 2007 stock incentive plan ( the amended and restated plan ) , and in may 2013 our shareholders ratified the amended and restated plan .
we currently have approximately 15.6 million shares of common stock reserved for future grants under the amended and restated plan .
options granted under the 2007 plan and the amended and restated plan are non-qualified and are granted at a price equal to the fair market value of our common stock at the date of grant .
generally , options granted have a term of seven to ten years from the date of grant , and vest in increments of 25% ( 25 % ) per year over a period of four years beginning on the first anniversary date of the grant .
options granted to non-employee directors have a term of ten years and are fully vested at the grant date .
in december 2008 , the board of directors amended and restated the republic services , inc .
2006 incentive stock plan ( formerly known as the allied waste industries , inc .
2006 incentive stock plan ) ( the 2006 plan ) .
allied 2019s shareholders approved the 2006 plan in may 2006 .
the 2006 plan was amended and restated in december 2008 to reflect republic as the new sponsor of the plan , to reflect that any references to shares of common stock are to shares of common stock of republic , and to adjust outstanding awards and the number of shares available under the plan to reflect the allied acquisition .
the 2006 plan , as amended and restated , provided for the grant of non- qualified stock options , incentive stock options , shares of restricted stock , shares of phantom stock , stock bonuses , restricted stock units , stock appreciation rights , performance awards , dividend equivalents , cash awards , or other stock-based awards .
awards granted under the 2006 plan prior to december 5 , 2008 became fully vested and nonforfeitable upon the closing of the allied acquisition .
no further awards will be made under the 2006 stock options we use a lattice binomial option-pricing model to value our stock option grants .
we recognize compensation expense on a straight-line basis over the requisite service period for each separately vesting portion of the award , or to the employee 2019s retirement eligible date , if earlier .
expected volatility is based on the weighted average of the most recent one year volatility and a historical rolling average volatility of our stock over the expected life of the option .
the risk-free interest rate is based on federal reserve rates in effect for bonds with maturity dates equal to the expected term of the option .
we use historical data to estimate future option exercises , forfeitures ( at 3.0% ( 3.0 % ) for 2014 and 2013 ) and expected life of the options .
when appropriate , separate groups of employees that have similar historical exercise behavior are considered separately for valuation purposes .
we did not grant stock options during the year ended december 31 , 2015 .
the weighted-average estimated fair values of stock options granted during the years ended december 31 , 2014 and 2013 were $ 5.74 and $ 5.27 per option , respectively , which were calculated using the following weighted-average assumptions: .

2014
2013
Expected volatility
27.5%
28.9%
Risk-free interest rate
1.4%
0.7%
Dividend yield
3.2%
3.2%
Expected life (in years)
4.6
4.5
Contractual life (in years)
7.0
7.0

.

Question: Analyse this data from a financial earnings document. what was the percentage change in the weighted-average estimated fair values of stock options granted from 2013 and 2014
Choices:
0.01692
1.88
89184.06072
0.08918
1
Correct choice index: 3