13. Stock-Based Compensation

On May 3, 2018, our shareholders approved the 2018 Omnibus Incentive Plan (the “Plan”), which was adopted by the Board of Directors on February 22, 2018, subject to shareholder approval. The Plan’s purpose is to promote the Company’s long-term financial interests and growth by attracting, retaining and motivating high quality key employees and directors, motivating such employees and directors to achieve the Company’s short- and long-range performance goals and objectives, and thereby align their interests with those of the Company’s shareholders. The Plan reserves 4,500,000 shares of common stock to be issued for grants of several different types of long-term incentives including stock options, stock appreciation rights, restricted awards, performance awards, other common stock-based awards, and dividend equivalent rights.

The 2013 Omnibus Incentive Plan (the “Previous Plan”), was replaced by the Plan, and no future grants may be made under the Previous Plan. However, any outstanding awards or grants made under the Previous Plan will continue until the end of their specified terms.

In the first half of 2018, our Board of Directors granted 0.2 million stock options, 0.1 million performance share units and 0.1 million restricted stock units.

We estimate the fair value of each stock option on the date of grant using the Black-Scholes option pricing model. The following table details the weighted-average grant-date fair values and the assumptions used for estimating the fair values of stock option grants made during the six months ended June 30, 2018:



	Stock Options
Weighted-average grant-date fair value	$	8.91
Expected life, in years		5.4
Risk-free interest rate		2.7	%
Expected volatility		39.7	%

The weighted average grant date fair value of our performance share units granted in the six months ended June 30, 2018, was $22.92. We measure the fair value of performance share units based on the closing market price of our common stock on the date of the grant. These shares are evaluated each reporting period for respective attainment rates against the performance criteria.

The weighted-average grant date fair value per unit for grants made during the six months ended June 30, 2018, was $22.27. We measure the fair value of restricted share units based on the closing market price of our common stock on the date of the grant. The restricted share units vest over three years.

We recognized stock-based compensation expense of $1.4 million and $3.8 million for the three and six months ended June 30, 2018, and $2.7 million and $5.4 million for the six months ended June 30, 2017. At June 30, 2018, unearned compensation cost related to the unvested portion of all stock-based compensation awards was approximately $9.7 million and is expected to be recognized over the remaining vesting period of the respective grants, through the first quarter of 2021.