. STOCK-BASED COMPENSATION PLANS

The 2016 Incentive Plan and the 2007 Incentive Plan (collectively "the 2016 and 2007 Plans") permit the award of restricted shares or restricted stock units to directors and key employees, including our officers who are from time to time responsible for the management, growth and protection of our business. Restricted shares granted under the 2016 and 2007 Plans generally vest either in full upon three years from the date of grant, on a pro-rata basis over a three year term or upon retirement at or after age 60. The fair value of restricted shares that vest solely based on continued service under the 2016 and 2007 Plans is determined by the product of the number of shares granted and the grant date market price of our common stock.

On September 22, 2015, the Board of Directors approved the adoption of the Executive Long-Term Incentive Compensation Plan (the "ELTI Plan"), pursuant to which certain named executive officers ("NEOs") and other key executives ("Grantees") may earn variable equity payouts based upon us achieving certain key performance metrics over a specified period. The ELTI Plan was adopted pursuant to 2016 and 2007 Plans, which were previously approved by our shareholders.

2017 Awards

On February 17, 2017, certain NEOs and Grantees received the following:


•	25,119 restricted stock units to NEOs vesting equally over three service periods ending December 31, 2017, December 31, 2018 and December 31, 2019;


•	28,467 performance share units ("PSU") to NEOs with vesting contingent on financial performance measures at the end of a 34-month performance period ending December 31, 2019; and


•	61,530 restricted stock shares to Grantees vesting equally over three service periods ending February 17, 2018, February 17, 2019 and February 17, 2020.

The performance criteria for the 2017 PSU awards are a cumulative Adjusted EBITDA target that was set at the beginning of the plan performance period for the entire three year period, and a cash flow metric that is the aggregate of the cash flow targets for the three individual years that is set annually at the beginning of each year. The cash flow metric is defined as cash flow from operating activities plus distributions of capital from equity investments less capital maintenance expenditures. The Compensation Committee can make adjustments as it may deem appropriate to these metrics. Measurement against these criteria will be determined against a payout curve which provides up to 200% of performance share units based on the original award.

The performance criteria also includes a relative total shareholder return ("TSR") component. Our TSR will be ranked versus the companies in the Russell 2000 index and will be calculated based on our relative placement within the Russell 2000 index. The PSU awards may be adjusted based on the Company’s TSR, by increasing the PSU awards by 25% if the Company’s TSR is in the top quartile, decreasing the PSU awards by 25% if the Company’s TSR is in the bottom quartile, and providing no change to the PSU awards if the Company’s TSR is in the middle two quartiles.

The total compensation cost we will recognize under the PSUs will be determined using the Monte Carlo valuation methodology and will be based upon an equal performance weighting for the two financial measures and then adjusted based on the Company’s TSR performance within the Russell 2000 index. The maximum number of PSUs that can be earned for a performance period is 250% of the original award.

We recognized stock-based compensation expense of $5.8 million for the three months ended September 30, 2017 and $17.5 million for the nine months ended September 30, 2017. We recognized stock-based compensation expense of $4.8 million for the three months ended September 30, 2016 and $14.3 million for the nine months ended September 30, 2016.