11. SHARE-BASED COMPENSATION

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Effective July 1, 2015, our eligible employees commenced participation in the 2015 LTIP.  The 2015 LTIP authorizes the Board to grant stock options, stock appreciation rights, restricted shares, restricted share units, performance awards, and dividend equivalents.  All grants are made by issuing new shares and no more than 4.0 million shares of common stock may be issued under the 2015 LTIP.  As of March 31, 2021, we had 2.0 million shares remaining available for issuance under the 2015 LTIP.

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Share-based compensation expense is included in selling, general, and administrative expense.  The income tax effect associated with share-based compensation awards is included in income tax expense.  The following table presents share-based compensation amounts recognized in our condensed consolidated statements of operations, in thousands:

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The following table presents a summary of our share-based compensation activity for the three months ended March 31, 2021, in thousands, except per share amounts:

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Unrecognized share-based compensation expense related to unvested awards is shown in the following table, dollars in thousands:

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Our RSAs with performance-based conditions are evaluated on a quarterly basis with adjustments to compensation expense based on the likelihood of the performance target being achieved or exceeded.  The following table shows the range of payouts and the related expense for our outstanding RSAs with performance-based conditions, in thousands:

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During the first quarter of 2021, RSAs with performance-based conditions that were granted on February 19, 2018 vested based on cumulative three-year achievement of 200%. Total compensation expense recognized over the three-year performance period, net of forfeitures, was $3.7 million.

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The fair value of our RSAs with a market-based condition granted under the 2015 LTIP was determined using a Monte Carlo simulation.  The following are key inputs in the Monte Carlo analysis for awards granted in 2021 and 2020:

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The fair values of stock options granted under the 2015 LTIP were calculated using the Black-Scholes Options Pricing Model.  The following table presents the assumptions used to estimate the fair values of stock options granted in 2021 and 2020:

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