The Company has a stock incentive plan, which is described below. The compensation cost that has been charged against income for the plan was approximately $1,100,000, $851,000 and $1,170,000 for the years ended December 31, 2019, 2018 and 2017, respectively.

Stock Incentive Plan

On March 23, 2009, the Company’s board of directors adopted the 2009 Stock Incentive Plan (the “Plan”), which was effective upon approval by the stockholders at the 2009 Annual Meeting of Stockholders. The 2009 Plan originally permitted the grant of up to 2,550,000 shares of common stock. However, upon stockholder approval during 2014, the Plan was amended in order to allow the Company to grant stock options for up to 5,550,000 shares of common stock. The Plan authorizes the grant of stock appreciation rights, restricted stock, incentive stock options, non-qualified stock options, non-stock share equivalents, performance shares or performance units and other equity-based awards. Option awards are generally granted with an exercise price equal to the estimated fair market value of the Company’s stock at the date of grant.

As of December 31, 2019, there are a total of 3,202,060 shares available to be granted under the Plan.

Stock-based compensation expense for stock-based compensation awards granted is based on the grant-date fair value. For stock option awards, the fair value is estimated at the date of grant using the Black-Scholes-Merton valuation model. This model requires the input of highly subjective assumptions, changes to which can materially affect the fair value estimate. The fair value of each option granted is estimated on the date of grant using the Black-Scholes-Merton model based on the weighted-average assumptions for expected dividend yield, expected stock price volatility, risk-free interest rate and expected life of options granted.

The assumptions used in determining the fair value of 2019, 2018 and 2017 stock option grants were as follows:

The weighted average grant-date fair value of options granted during the years ended December 31, 2019, 2018 and 2017 was $12.40, $12.76 and $11.82, respectively.

The following tables summarize stock option activity:

Exercisable options at December 31, 2019 were as follows:

As of December 31, 2019, there was $1.3 million of total unrecognized compensation cost related to non-vested stock options. As of December 31, 2019, non-vested stock options had a weighted average remaining time to vest of 1.3 years.

Restricted Stock

The Company periodically grants restricted stock awards that vest upon service conditions. Dividend payments are made during the vesting period.

The following table summarizes restricted stock activity:

The value of restricted stock is determined to be the current value of the Company’s stock, and this total value will be recognized as compensation expense over the vesting period. As of December 31, 2019, there was $1.4 million of total unrecognized compensation cost related to non-vested restricted stock. As of December 31, 2019, non-vested restricted stock had a weighted average remaining time to vest of 2.5 years.

Retirement Plans

The Company has a retirement savings 401(k) and profit-sharing plan in which all employees age 21 and older may participate after completion of one year of service. For employees in service with the Company at June 15, 2005, the length of service and age requirements were waived. The Company matches employees’ contributions based on a percentage of salary contributed by participants and may make additional discretionary profit-sharing contributions. The Company’s expense for the plan was $1.7 million, $1.5 million and $1.4 million for 2019, 2018 and 2017, respectively.