During 2021, the Company’s compensation committee approved the 2021 Long-Term Incentive Plan, which supersedes the 2015 Long-Term Incentive Plan, and authorizes restricted time and performance awards and stock options to key employees. The Company's stock-based compensation program is a long-term retention program that provides for the grant of options, restricted stock, restricted stock units (“RSUs”), performance-based restricted stock or units (“PSUs”) and/or market stock units (“MSUs”) to attract, retain and provide incentives for directors, officers and employees. The maximum number of shares reserved for the grant of awards under the plan is 4.7 million, with approximately 3.7 million shares available as of December 31, 2023. The Company settles stock-based awards with newly issued shares.

Restricted stock is shares of stock granted to an employee, non-employee director or other service providers for which sale is prohibited for a specified period of time. Restricted stock typically vests ratably over a one or three-year period following the date of grant. RSUs represent a promise to deliver shares to the employee, non-employee director or other service providers at a future date if certain vesting conditions are met. RSUs typically vest ratably over a three-year period following the date of grant. The Company does not deliver the shares associated with the RSUs to the employee, non-employee director or other service providers until the vesting conditions are met. The number of shares or units granted are determined based upon the closing price of the Company's common stock on the date of the award.

MSUs represent a promise to deliver shares to the employee, non-employee director or other service providers at a future date if certain performance and vesting conditions are met. The MSUs are market-based equity incentive awards based on a performance-multiplier of change in the stock price of the Company’s common stock between the grant date and a determined closing price. Each MSU represents the right to receive one share of Company stock multiplied by a performance multiplier or, at the option of the Company, an amount of cash. The number of shares that will eventually be earned and vest may be more or less than the number of MSUs that are awarded, depending on the Company's common stock price. Awards, if earned, will vest after a determined performance period and may be earned at a level ranging from 0%-150% of the number of MSUs granted, depending on performance. The number of units granted were determined based upon the closing price of the Company's common stock on the date of the award.

The Company assessed the applicable metrics related to the MSU grants, estimating the fair value of employee MSU awards and the amount of stock compensation expense using the Monte-Carlo pricing model.

PSUs represent a promise to deliver shares to the employee, non-employee director or other service providers at a future date if certain performance and vesting conditions are met. PSUs generally vest three years following the date of grant based on the attainment of performance- or market-based goals, all of which are subject to a service condition. The Company does not deliver the shares associated with the PSUs to the employee, non-employee director or other service providers until the performance and vesting conditions are met.

The PSUs granted may be earned based on the Company's performance against metrics relating to annual Adjusted EBITDA and annual revenue. Awards, if earned, will vest after a three-year performance period and may be earned at a level ranging from 0%-200% of the number of PSUs granted, depending on performance. The number of units were determined based upon the closing price of the Company's common stock on the date of the award. The Company assessed the applicable metrics related to the PSU grants, determined the blended probability of achieving the performance metrics and valued the awards based on the fair value at the date of grant with the amount of stock compensation expense determined based on the number of PSU’s expected to vest.

See the following table for a summary of PSU, restricted stock, RSU and MSU activity.

Stock options represent a right to buy a number of shares by the employee, non-employee director or other service providers at a future date, for a pre-set price, or exercise price, for a fixed period of time. Stock options generally vest over one to four years, with a term of ten years. Stock compensation expense related to options are recorded based on the fair value of stock option grants, amortized on a straight-line basis over the employee’s required service period. The Company estimated the fair value of employee stock options using the Black-Scholes option pricing model. The Company uses the simplified method for determining an option term under Black-Sholes as the Company issues options infrequently. The fair values of employee stock options granted under the 2021 and 2015 plans were estimated using the following assumptions:

During the year ended 2022, 77,500 options with an intrinsic value of $0.3 million were exercised, and during the year ended December 31, 2021, 12,000 options with an intrinsic value of $0.1 million were exercised. No options were exercised during the year ended December 31, 2023.

Stock-based compensation expense for the years ended December 31, 2023, 2022 and 2021 was $13.9 million, $7.0 million and $5.6 million, respectively, and is included in general and administrative expenses. The total income tax benefit recognized for stock-based compensation plans for the years ended December 31, 2023, 2022 and 2021 was $0.0 million. As of December 31, 2023, unrecognized stock-based compensation expense was $16.6 million. This amount is expected to be recognized over a weighted average period of approximately 2.1 years.

Mr. Bressler has an equity incentive opportunity to earn an award of options based on the financial performance of Natural Habitat, where if the final year equity value of Natural Habitat, as defined in Mr. Bressler's employment agreement, as amended, exceeds $25.0 million, effective as of December 31, 2025, Mr. Bressler will be granted options with a fair value equal to 10.1% of such excess, subject to certain conditions. Mr. Bressler has a one-time right to elect an early option award of 50% valued as of December 31, 2023, by providing notice within 30 days of being provided with the final value calculation. The actual number of options granted will be determined by the calculated final year equity value of Natural Habitat and the Black-Scholes per share option value, factoring in the Company’s stock price on the date of the grant, its volatility and a discount rate. During the year ended December 31, 2023, the Company determined it was probable the performance condition would be met and therefore, recorded $8.0 million of stock-based compensation expense.

In 2021, Mr. Lawrence, President of Off the Beaten Path, was issued 1,007 profit interest units in the equity of Off the Beaten Path as part of the 2021 acquisition. The profit interest units had a grant date fair value of $132.86 per share and are considered vested upon issuance.