For the years ended December 31, 2016, 2015 and 2014, equity-based compensation expense was $2.7 million, $2.7 million and $2.6 million, respectively. We have outstanding awards granted pursuant to three shareholder approved equity-based compensation plans: the Long Term Incentive Plan (1999 Plan) the 2006 Long Term Incentive Plan (2006 Plan) and the 2014 Stock and Incentive Plan (2014 Plan). The 1999 Plan was terminated and replaced by the 2006 Plan. The 2006 Plan was terminated and replaced by the 2014 Plan. Equity-based awards outstanding under the 1999 and 2006 Plan remain in effect, but no new awards may be granted under those plans. A total of 6.3 million shares of our common stock have been reserved for issuance through the plans. Stock options and stock-settled stock appreciation rights (SARs) are generally granted with an exercise price equal to the market price of our common stock on the date of grant; the awards generally vest over four years of continuous service and have a contractual term of ten years. Grants of non-vested restricted stock awards to employees generally vest over four years of continuous service and grants to non-employee directors generally vest over one year. Certain awards provide for accelerated vesting if there is a change in control (as defined in the plans).

The recipient of a SAR is generally entitled to receive, upon exercise and without payment to us (but subject to required tax withholdings), that number of shares having an aggregate fair market value as of the date of exercise multiplied by an amount equal to the excess of the fair market value per share on the date of exercise over the fair market value per share at the date of the grant.

Use of a valuation model requires us to make certain assumptions with respect to selected model inputs. Changes in these input variables would affect the amount of expense associated with equity-based compensation. Expected volatility is based on the historical volatility of our common shares over the expected term of the stock option or SAR. Expected term is based on historical exercise and employee termination data and represents the period of time that options and SARs are expected to be outstanding. The risk-free interest rate is based on U.S. Treasury Daily Treasury Yield Curve Rates corresponding to the expected life assumed at the date of grant. Dividend yield is zero as there are no payments of dividends made or expected. The fair value of non-vested restricted stock awards is based on the fair market value of the shares awarded at the date of grant multiplied by the number of shares awarded.

The weighted average assumptions to estimate the grant date fair value of stock options and SARs, including those with market conditions, are summarized as follows:

A summary of stock option and SARs activity as of and for the year ended December 31, 2016 follows (shares in thousands):

As of December 31, 2016, stock options and SARs are further summarized as follows (shares and dollars in thousands):

The weighted average grant-date fair value of stock options and SARs granted during the years ended December 31, 2016, 2015 and 2014 was $2.85, $3.04, and $6.45, respectively.

Stock option and SARs exercise data is summarized as follows (in thousands):

Non-vested restricted stock award activity for the year ended December 31, 2016 is summarized as follows (shares in thousands):

The total fair value of non-vested restricted shares that vested during the years ended December 31, 2016, 2015 and 2014 was $1.5 million, $2.0 million, and $1.1 million, respectively.

As of December 31, 2016, 0.7 million shares remain available for grant under the 2014 Plan. Shares available from prior plans were transferred to the successor plan. No shares remain available under any prior plans. Total unrecognized compensation costs related to all non-vested equity-based compensation arrangements was $6.2 million as of December 31, 2016 and is expected to be recognized over a weighted-average period of 1.9 years.