pre_text: The Monte Carlo simulation assumptions used for the periods presented were as follows: As of January 3, 2020, there was $12 million of unrecognized compensation cost, net of estimated forfeitures, which is expected to be recognized over a weighted average period of 1.7 years. The fair value of performance-based stock awards that vested in fiscal 2019, 2018 and 2017 was $9 million, $13 million, and $4 million, respectively.
table: Year Ended
table: January 3, 2020 December 28, 2018 December 29, 2017
table: Expected volatility 22.02% 25.37% 27.19%
table: Risk free rate of return 2.39% 2.35% 1.53%
table: Weighted average grant date stock price $62.66 $65.00 $53.73
question: Analyse this data from a financial earnings document. What was the change in the Expected volatility from 2017 to 2018?