For the three-month periods ended September 30, 2021 and 2020, our total stock-based compensation expense, which includes reversals of expense for certain forfeited or cancelled awards, was approximately $108,000 and $63,000, respectively. For the nine-month periods ended September 30, 2021 and 2020, our total stock-based compensation expense, which includes reversals of expense for certain forfeited or cancelled awards, was approximately $372,000 and $136,000, respectively. We have not recorded any income tax benefit related to stock-based compensation in any of the three-month or nine-month periods ended September 30, 2021 and 2020.

A summary of the status of our stock options as of September 30, 2021, and changes during the nine-month period then ended, is presented below.

The weighted average grant date fair value per stock option granted during the nine-month period ended September 30, 2021 was $1.86. Key assumptions used in the Black-Scholes option pricing model for stock options granted during the nine-month period ended September 30, 2021 were the Company’s stock price, an expected volatility rate of 90.34%, a risk-free rate of 0.67%, and an expected life of 5.97 years. 

A summary of the status of our unvested restricted stock as of September 30, 2021, and changes during the nine-month period then ended, is presented below.

As of September 30, 2021, there was approximately $333,000 of total unrecognized compensation expense related to unvested stock-based awards, which we expect to recognize over the remaining weighted average vesting term of 1.4 years.