Restricted Stock Units:
A summary of restricted stock activity for the fiscal year ended January 31, 2019 is as follows:
(1) Based on Autodesk's financial results and relative total stockholder return for the fiscal 2018 performance period. The performance stock units were attained at rates ranging from 90.0% to 117.6% of the target award.
For the restricted stock granted during fiscal years ended January 31, 2019, 2018, and 2017, the weighted average grant date fair values were $144.37, $106.55, and $65.95, respectively. The fair values of the shares vested during fiscal years ended January 31, 2019, 2018, and 2017 were $425.4 million, $399.7 million, and $232.2 million, respectively.
During the fiscal year ended January 31, 2019, Autodesk granted 2.1 million restricted stock units. Restricted stock units
vest over periods ranging from immediately upon grant to a pre-determined date that is typically within three years from the
date of grant. Restricted stock units are not considered outstanding stock at the time of grant, as the holders of these units are
not entitled to any of the rights of a stockholder, including voting rights. The fair value of the restricted stock units is expensed
ratably over the vesting period. Autodesk recorded stock-based compensation expense related to restricted stock units of $189.3
million, $202.1 million, and $173.0 million during fiscal years ended January 31, 2019, 2018, and 2017, respectively. As of
January 31, 2019, total compensation cost not yet recognized of $364.5 million related to non-vested awards is expected to be
recognized over a weighted average period of 1.76 years. At January 31, 2019, the number of restricted stock units granted but
unvested was 3.9 million.
During the fiscal year ended January 31, 2019, Autodesk granted 0.2 million performance stock units for which the ultimate number of shares earned is determined based on the achievement of performance criteria at the end of the stated service and performance period. The performance criteria for the performance stock units are based on Annualized Recurring Revenue ("ARR") and free cash flow per share goals adopted by the Compensation and Human Resources Committee, as well as total stockholder return compared against companies in the S&P Computer Software Select Index or the S&P North American Technology Software Index ("Relative TSR"). These performance stock units vest over a three-year period and have the following vesting schedule:
Up to one third of the performance stock units may vest following year one, depending upon the achievement of the performance criteria for fiscal 2019 as well as 1-year Relative TSR (covering year one).
Up to one third of the performance stock units may vest following year two, depending upon the achievement of the performance criteria for year two as well as 2-year Relative TSR (covering years one and two).
Up to one third of the performance stock units may vest following year three, depending upon the achievement of the performance criteria for year three as well as 3-year Relative TSR (covering years one, two and three).
Performance stock units are not considered outstanding stock at the time of grant, as the holders of these units are not entitled to any of the rights of a stockholder, including voting rights. Autodesk has determined the grant-date fair value for these awards using the stock price on the date of grant or if the awards are subject to a market condition, a Monte Carlo simulation model. The fair value of the performance stock units is expensed using the accelerated attribution over the vesting period. Autodesk recorded stock-based compensation expense related to performance stock units of $28.6 million, $33.7 million, and $22.9 million during fiscal years ended January 31, 2019, 2018, and 2017 respectively. As of January 31, 2019, total compensation cost not yet recognized of $5.6 million related to unvested performance stock units, is expected to be recognized over a weighted average period of 0.81 years. At January 31, 2019, the number of performance stock units granted but unvested was 0.4 million.
Table:
 | Unreleased Restricted Stock Units (in thousands) | Weighted average grant date fair value per share
Unvested restricted stock at January 31, 2018 | 5,670.7 | $82.94
Granted | 2,250.7 | 144.37
Vested | (2,982.0) | 76.30
Canceled/Forfeited | (681.9) | 94.70
Performance Adjustment (1) | 29.9 | 101.74
Unvested restricted stock at January 31, 2019 | 4,287.4 | $120.07


Question: What is the performance criteria for the performance stock units?
Answer: The performance criteria for the performance stock units are based on Annualized Recurring Revenue ("ARR") and free cash flow per share goals adopted by the Compensation and Human Resources Committee, as well as total stockholder return compared against companies in the S&P Computer Software Select Index or the S&P North American Technology Software Index ("Relative TSR").