We use a variety of compensation programs to attract, retain and motivate our employees, and to more closely align employee compensation with company performance. These programs include, but are not limited to, short-term incentive awards tied to performance goals, cash awards to inventors for filed patent applications and patent issuances, and long-term incentives in the form of stock option awards, time-based RSU awards, performance-based RSU awards and cash awards.

Our long-term incentives typically include annual time-based RSU grants or cash awards with a three-year vesting period, as well as annual performance-based RSU grants or cash awards with a three to five-year performance period; as a result, in any one year, we are typically accounting for at least three active cycles. Additionally, from time to time, executive officers are awarded long term incentives or new hire grants that may include time-based RSUs, performance-based RSUs or options. We issue new shares of our common stock to satisfy our obligations under the share-based components of these programs. However, our Board of Directors has the right to authorize the issuance of treasury shares to satisfy such obligations in the future.

On June 14, 2017, our shareholders adopted and approved the 2017 Equity Incentive Plan (the "2017 Plan"), under which officers, employees, non-employee directors and consultants can receive share-based awards such as RSUs, restricted stock and stock options as well as other stock or cash awards. The plan was amended in order to reserve an additional 1.8 million shares of our common stock for issuance under the 2017 Plan. Such amendment was adopted and approved by our shareholders on June 2, 2021.

From June 2009 through June 14, 2017, we granted equity awards pursuant to our 2009 Stock Incentive Plan (the “2009 Plan," and, together with the 2017 Plan, the "Equity Plans"), which was adopted and approved by our shareholders on June 4, 2009, and the material terms of which were re-approved on June 12, 2014. Upon the adoption of the 2017 Plan, the 2009 Plan was terminated and all shares remaining available for grant under the 2009 Plan were canceled. The number of shares available for issuance under the 2017 Plan, as amended, is equal to 4.2 million shares plus any shares subject to awards granted under the 2009 Plan that, on or after June 14, 2017, expire or otherwise terminate without having been exercised in full, or that are forfeited to or repurchased by us.

We may issue RSUs to officers, employees, non-employee directors and consultants. Any cancellations of unvested RSUs granted under the Equity Plans will increase the number of shares remaining available for grant under the 2017 Plan. Time-based RSUs vest over periods generally ranging from 1 to 3 years from the date of the grant. Performance-based RSUs generally have a vesting period between 3 and 5 years. Milestone performance-based RSUs may vest at any time, upon achievement of the milestone goal, during the performance period, which is typically 5 years.

As of December 31, 2023, we had unrecognized compensation cost related to share-based awards of $27.8 million, at current performance accrual rates. For time-based grants with graded vesting, we expect to amortize the associated unrecognized compensation cost using an accelerated method. For time-based grants that cliff vest, we expect to amortize the associated unrecognized compensation cost as of December 31, 2023, on a straight-line basis generally over the remaining vesting period.

Vesting of performance-based RSU awards is subject to attainment of specific goals established by the Human Capital Committee of the Board of Directors. Depending upon performance achievement against these goals, the number of shares that vest can be anywhere from 0 to 3 times the target number of shares.

Information with respect to current RSU activity is summarized as follows (in thousands, except per share amounts):


	Number of Unvested RSUs	Weighted Average Per Share Grant Date Fair Value
Balance at December 31, 2022	1,180	$	53.36
Granted*	535	73.80
Forfeited	(197)	55.07
Vested	(410)	54.95
Balance at December 31, 2023	1,108	$	62.34

* These numbers include fewer than 0.1 million RSUs credited on unvested RSU awards as dividend equivalents. Dividend equivalents accrue with respect to unvested RSUs when and as cash dividends are paid on the Company's common stock, and vest if and when the underlying RSUs vest. Granted amounts include performance-based RSU awards at their maximum potential payout.

During 2023, 2022 and 2021, we granted approximately 0.5 million, 0.7 million and 0.5 million RSUs under the Equity Plans, respectively, with weighted-average per share grant date fair values of $73.80, $55.15 and $68.44, respectively, assuming target payout for the performance-based awards. The total vest date fair value of the RSUs that vested in 2023, 2022 and 2021 was $31.0 million, $25.3 million and $22.6 million, respectively. The weighted average per share grant date fair value of the awards that vested in 2023, 2022 and 2021 was $54.95, $67.29 and $62.44, respectively.

The 2009 Plan allowed, and the 2017 Plan allows, for the granting of incentive and non-qualified stock options, as well as other securities. The administrator of the Equity Plans, the Human Capital Committee of the Board of Directors, determines the number of options to be granted, subject to certain limitations set forth in the 2017 Plan. We grant stock options to a limited number of the employee base annually as part of our long-term incentive programs, which have generally vested over three years. During the year ended December 31, 2018, performance-based options were granted for the first time. The number of performance-based options which vest, if at all, is anywhere from 0 to 3 times the target number of options subject to the attainment of performance goals measured either during or at the end of the performance period. Performance-based options typically have a vesting period between three and five years. Milestone performance options may vest at any time, upon achievement of the milestone goal, during the performance period, which is typically 5 years.

Under the terms of the Equity Plans, the exercise price per share of each option, other than in the event of options granted in connection with a merger or other acquisition, cannot be less than 100% of the fair market value of a share of common stock on the date of grant. Options granted under the Equity Plans are generally exercisable for a period of between 7 to 10 years from the date of grant and may vest on the grant date, another specified date, over a period of time and/or dependent upon the attainment of specified performance goals. We also have less than 0.1 million options outstanding under a prior stock plan that do not expire.

The fair value for option awards is computed using the Black-Scholes pricing model, whose inputs and assumptions are determined as of the date of grant and which require considerable judgment. Expected volatility was based upon a combination of implied and historic volatilities. The weighted-average grant date fair value per option award granted during the years ended December 31, 2023, 2022 and 2021 was $24.41, $20.28, and $23.04, respectively, based upon the assumptions included in the table below:

The weighted average remaining contractual life of our outstanding options was 8.6 years as of December 31, 2023. Options with an indefinite contractual life, which were granted between 1983 and 1986 under a prior stock plan, were assigned an original life in excess of 50 years for purposes of calculating the weighted average remaining contractual life. The majority of these options have an exercise price between $9.00 and $11.63.

The total intrinsic value of our outstanding options as of December 31, 2023 was $29.2 million. Of the 0.7 million outstanding options as of December 31, 2023, 0.3 million were exercisable with a weighted-average exercise price of $61.33. Options exercisable as of December 31, 2023, had total intrinsic value of $12.9 million and a weighted average remaining contractual life of 9.4 years. The total intrinsic value of stock options exercised during the years ended December 31, 2023, 2022 and 2021 was $5.4 million, $0.3 million and $3.6 million, respectively. In 2023, we recorded cash received from the exercise of options of $1.3 million. Upon option exercise, we issued new shares of stock.

As of December 31, 2023, we had unrecognized compensation cost on our unvested stock options of $2.5 million, at current performance accrual rates. As of December 31, 2023 and 2022, we had approximately 0.7 million and 0.1 million options outstanding, respectively, that had exercise prices less than the fair market value of our stock at the respective balance sheet date. These options would have generated cash proceeds to the Company of $46.7 million and $1.1 million, respectively, if they had been fully exercised on those dates.

We have a 401(k) plan (“Savings Plan”) wherein employees can elect to defer compensation within federal limits. We match a portion of employee contributions. Our 401(k) contribution expense was approximately $1.1 million, $1.2 million and $1.3 million for 2023, 2022 and 2021, respectively. Additionally, the company contributed $0.3 million, $0.2 million and $3.4 million in 2023, 2022 and 2021, respectively, to other defined contribution plans, including InterDigital’s Deferred Compensation Plan (“Deferred Plan”).