13. Stock‑Based Compensation

2010 Stock Incentive Plan

In in May 2010, the Company’s Board of Directors and stockholders adopted the 2010 Stock Incentive Plan (the “2010 Plan”). The material terms of the performance goals under the 2010 Plan, as amended and restated, were approved by stockholders at the Company’s 2014 annual meeting of stockholders and the plan’s term was extended further by the stockholders at the Company’s 2020 annual meeting of stockholders. The 2010 Plan provides for the issuance of nonqualified stock options, incentive stock options, stock appreciation rights, restricted stock awards and restricted stock units, any of which may be performance‑based, and for incentive bonuses, which may be paid in cash or stock or a combination of both, to eligible employees, officers, non‑employee directors and other service providers to the Company and its subsidiaries. A maximum of 2,130,000 shares of common stock may be issued pursuant to all awards under the 2010 Plan. As of December 31, 2023, the Company had 340,160 shares of common stock available for future issuance of awards under the 2010 Plan. The shares of common stock to be issued under the 2010 Plan will be made available from authorized and unissued Company common stock.

Restricted Stock Units

Restricted stock units (“RSUs”) are granted to both non‑employee directors and management. Prior to 2013, RSUs were only issued to directors. However, in 2013, the Company changed the timing and form of management’s annual stock grants and began to grant RSUs to management.  RSUs do not carry voting rights. While all non-employee director RSUs participate in dividend equivalents, there are two classes of management RSUs, one that participates in dividend equivalents, and a second that does not participate in dividend equivalents. Each RSU represents the right to receive one share of the Company’s common stock and is subject to time based vesting restrictions. Participants are not required to pay any consideration to the Company at either the time of grant of a RSU or upon vesting.

In 2013, the Company’s compensation committee approved a retirement provision for RSUs issued to management. The retirement provision provides that members of management who either (1) are age 65 or older or (2) have at least ten years of service and are at least age 55 will continue to vest in unvested RSUs upon retirement. As the retirement provision does not qualify as a substantive service condition, the Company incurred $1,887, $3,724 and $2,988 in additional expense related to each year's grant in the years ended December 31, 2023, 2022 and 2021, respectively, as a result of accelerated stock based compensation expense for employees who meet the thresholds of the retirement provision. The Company’s nominating and governance committee also approved a retirement provision for the RSUs issued to non‑employee directors that accelerates the vesting of such RSUs upon retirement. Such awards are fully expensed immediately upon grant in accordance with ASC 718, as the retirement provision eliminates substantive service conditions associated with the awards.

A summary of RSU activity for the years ended December 31, 2023, 2022 and 2021 is as follows:

The Company recognized $3,700, $2,947 and $3,292 of compensation expense related to the RSU awards in the years ended December 31, 2023, 2022 and 2021, respectively. The unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares that were, as of December 31, 2023, expected to be earned through the requisite service period was approximately $2,474 and is expected to be recognized through 2026.

Beginning in 2019, grants to non-employee directors, vesting occurs as of the grant date. Vested director RSUs are “settled” by the delivery to the participant or a designated brokerage firm of one share of common stock per vested RSU as soon as reasonably practicable following a termination of service of the participant that constitutes a separation from service, or as soon as reasonably practicable upon grant if such election is made by the non-employee director, and in all events no later than the end of the calendar year in which such termination of service occurs or, if later, two and one‑half months after such termination of service. Vested management RSU’s are “settled” by the delivery to the participant or a designated brokerage firm of one share of common stock per vested RSU as soon as reasonably practicable following vesting.

Performance Share Unit Awards

The Company granted performance share units as performance based awards under the 2010 Plan in the first quarter of 2023, 2022 and 2021 that are subject to performance conditions over a three year performance period beginning in the year of the grant. Upon meeting the prescribed performance conditions, employees will be issued shares which vest immediately at the end of the measurement period. Currently the Company expects participants to earn 42,555, 24,688 and 29,888 shares related to the 2023, 2022 and 2021 performance share grants, respectively. In accordance with ASC 718, such awards are being expensed over the vesting period from the date of grant through the requisite service period, based upon the most probable outcome. In the first quarter of 2023 there were 16,502 performance share units that converted into RSUs related to the 2020 performance share grants. The fair value per share of the awards is the closing stock price on the date of grant, which was $37.36, $37.57 and $49.96 for the 2023, 2022 and 2021 grants, respectively. The Company recognized ($2,747), $3,783 and $2,502 of compensation expense related to the awards in the years ended December 31, 2023, 2022 and 2021, respectively. The unrecognized compensation expense calculated under the fair value method for shares that were, as of December 31, 2023, expected to be recognized through the requisite service period was $776 and is expected to be recognized through 2026.