STOCK-BASED COMPENSATION

The 2014 Incentive Plan is Ameren’s long-term stock compensation plan for eligible employees and directors. The 2006 Incentive Plan was replaced prospectively for new grants beginning in April 2014. The 2014 Incentive Plan provides for a maximum of 8 million common shares to be available for grant to eligible employees and directors. To the extent that the issuance of a share that is subject to an outstanding award under the 2006 Incentive Plan would cause Ameren to exceed the maximum authorized shares under the 2006 Incentive Plan, the issuance of that share will take place under the 2014 Incentive Plan. This will reduce the maximum number of shares that may be granted under the 2014 Incentive Plan. The 2014 Incentive Plan awards may be stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance share units, cash-based awards, and other stock-based awards.

A summary of nonvested shares at December 31, 2015, and changes during the year ended December 31, 2015, under the 2006 Incentive Plan and the 2014 Incentive Plan are presented below:



	Performance Share Units
	Share Units		Weighted-average Fair Value per Share Unit
Nonvested at January 1, 2015	1,162,377		$	35.35
Granted^(a)	570,313		52.88
Forfeitures	(1,944	)	34.75
Earned and vested^(b)	(705,876	)	33.93
Nonvested at December 31, 2015	1,024,870		$	46.08


(a)	Includes performance share units (share units) granted to certain executive and nonexecutive officers and other eligible employees in 2015 under the 2014 Incentive Plan.


(b)	Includes share units granted in 2013 that vested as of December 31, 2015, that were earned pursuant to the terms of the award grants. Also includes share units that vested due to attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees will vary depending on actual performance over the three-year measurement period.

Ameren recorded compensation expense of $19 million, $19 million, and $20 million for the years ended December 31, 2015, 2014, and 2013, respectively, and a related tax benefit of $7 million, $7 million, and $8 million for the years ended December 31, 2015, 2014, and 2013, respectively. Ameren settled performance share units of $27 million, $33 million, and $11 million for the years ended December 31, 2015, 2014, and 2013. There were no significant compensation costs capitalized related to the performance share units during the years ended December 31, 2015, 2014, and 2013. As of December 31, 2015, total compensation cost of $21 million related to nonvested awards not yet recognized is expected to be recognized over a weighted-average period of 23 months.

Performance Share Units

A share unit vests and entitles an employee to receive shares of Ameren common stock (plus accumulated dividends) if, at the end of the three-year performance period, certain specified performance or market conditions have been met and if the individual remains employed by Ameren through the required vesting period. The exact number of shares issued pursuant to a share unit varies from 0% to 200% of the target award, depending on actual company performance relative to the performance goals. The vesting period for share units awarded in 2015 extended beyond the three-year performance period to the payout date, while the vesting period for share units awarded in 2013 and 2014 matched the three-year performance period.

The fair value of each share unit awarded in 2015 under the 2014 Incentive Plan was determined to be $52.88, which was based on Ameren's closing common share price of $46.13 at December 31, 2014, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren's total shareholder return for a three-year performance period relative to the designated peer group beginning January 1, 2015. The simulations can produce a greater fair value for the share unit than the applicable closing common share price because they include the weighted payout scenarios in which an increase in the share price has occurred. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 1.10%, volatility of 12% to 18% for the peer group, and Ameren's attainment of a three-year average earnings per share threshold during the performance period.

The fair value of each share unit awarded in 2014, excluding the grants issued in April 2014 for certain executive officers, under the 2006 Incentive Plan and the 2014 Incentive Plan was determined to be $38.90, which was based on Ameren’s closing common share price of $36.16 at December 31, 2013, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren’s total shareholder return for a three-year performance period relative to the designated peer group beginning January 1, 2014. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 0.78%, volatility of 12% to 18% for the peer group, and Ameren’s attainment of a three-year average earnings per share threshold during the performance period.