STOCK-BASED COMPENSATION

Under the Company's 2004 Stock Incentive Plan ("2004 Plan"), the Company granted options to purchase shares of the Company's common stock at the fair market value on the date of grant. The options vested over periods up to three years and have a term of 10 years from date of grant. At its November 2007 meeting, the Company's Compensation Committee decided that restricted common stock awards and stock units ("restricted stock") would be awarded in place of stock options for long-term incentive award grants to employees. Restricted stock granted to employees generally vests 50% after two years and the remainder after three years from the date of grant. Restricted stock granted to non-employee directors generally vests on the first anniversary date of the grant. In February 2014, the Company's Board of Directors replaced the expired 2004 Plan by adopting the BorgWarner Inc. 2014 Stock Incentive Plan ("2014 Plan"). On April 30, 2014, the Company's stockholders approved the 2014 Plan. Under the 2014 Plan, approximately 8 million shares are authorized for grant, of which approximately 4.9 million shares are available for future issuance as of December 31, 2017.

Stock Options A summary of the plans’ shares under option at December 31, 2017, 2016 and 2015 is as follows:



	Shares (thousands)		Weighted average exercise price		Weighted average remaining contractual life (in years)	Aggregate intrinsic value (in millions)
Outstanding at January 1, 2015	1,714		$	16.11	1.7	$	66.5
Exercised	(440	)	$	14.76		$	19.2
Forfeited	(7	)	$	14.52
Outstanding at December 31, 2015	1,267		$	16.59	0.9	$	33.7
Exercised	(794	)	$	16.07		$	14.4
Outstanding at December 31, 2016	473		$	17.47	0.1	$	10.4
Exercised	(473	)	$	17.47		$	10.4
Outstanding at December 31, 2017	—		$	—	0.0	$	—

Options exercisable at December 31, 2017	—		$	—	0.0	$	—

Proceeds from stock option exercises for the years ended December 31, 2017, 2016 and 2015 were as follows:



	Year Ended December 31,
(millions of dollars)	2017		2016		2015
Proceeds from stock options exercised — gross	$	8.3	$	12.7	$	6.5
Tax benefit	8.2		0.3		10.3
Proceeds from stock options exercised, net of tax	$	16.5	$	13.0	$	16.8

Restricted Stock The value of restricted stock is determined by the market value of the Company’s common stock at the date of grant. In 2017, restricted stock in the amount of 776,753 shares and 26,919 shares was granted to employees and non-employee directors, respectively. The value of the awards is recognized as compensation expense ratably over the restriction periods. As of December 31, 2017, there was $28.0 million of unrecognized compensation expense that will be recognized over a weighted average period of approximately 2 years.

Restricted stock compensation expense recorded in the Consolidated Statements of Operations is as follows:



	Year Ended December 31,
(millions of dollars, except per share data)	2017		2016		2015
Restricted stock compensation expense	$	27.0	$	26.7	$	28.0
Restricted stock compensation expense, net of tax	$	19.7	$	19.5	$	20.4

A summary of the status of the Company’s nonvested restricted stock for employees and non-employee directors at December 31, 2017, 2016 and 2015 is as follows:



	Shares subject to restriction (thousands)		Weighted average grant date fair value
Nonvested at January 1, 2015	1,266		$	43.57
Granted	687		$	58.45
Vested	(588	)	$	39.14
Forfeited	(39	)	$	50.85
Nonvested at December 31, 2015	1,326		$	53.18
Granted	724		$	30.07
Vested	(551	)	$	47.55
Forfeited	(70	)	$	43.05
Nonvested at December 31, 2016	1,429		$	44.12
Granted	804		$	40.10
Vested	(521	)	$	56.53
Forfeited	(119	)	$	38.97
Nonvested at December 31, 2017	1,593		$	38.86

Total Shareholder Return Performance Share Plans The 2004 and 2014 Plans provide for awarding of performance shares to members of senior management at the end of successive three-year periods based on the Company's performance in terms of total shareholder return relative to a peer group of automotive companies. Based on the Company’s relative ranking within the performance peer group, it is possible for none of the awards to vest or for a range up to the 200% of the target shares to vest.

The Company recognizes compensation expense relating to its performance share plans ratably over the performance period regardless of whether the market conditions are expected to be achieved. Compensation expense associated with the performance share plans is calculated using a lattice model (Monte Carlo simulation). The amounts expensed under the plan and the common stock issuances for the three-year measurement periods ended December 31, 2017, 2016 and 2015 were as follows:



	Year Ended December 31,
(millions of dollars, except share data)	2017		2016		2015
Expense	$	9.9	$	9.6	$	12.2
Number of shares	—		—		—

The Company’s non-vested total shareholder return performance share awards outstanding at December 31, 2017, 2016 and 2015 were 356,750; 409,600; and 474,600 shares, respectively. The weighted average grant date fair value of the total shareholder return performance share awards was $32.26, $43.99 and $56.55 for 2017, 2016 and 2015, respectively. As of December 31, 2017, there was $7.2 million of unrecognized compensation expense that will be recognized over a weighted average period of approximately 2 years.

Relative Revenue Growth Performance Share Plans In the second quarter of 2016, the Company started a new performance share program to reward members of senior management based on the Company's performance in terms of revenue growth relative to the vehicle market over three-year performance periods. The value of this performance share award is determined by the market value of the Company’s common stock at the date of grant. The Company recognizes compensation expense relating to its performance share plans over the performance period based on the number of shares expected to vest at the end of each reporting period. The actual performance of the Company is evaluated quarterly, and the expense is adjusted according to the new projections. The amounts expensed under the plan and common stock issuance for the year ended December 31, 2017 and 2016 were as follows:



	Year Ended December 31,
(millions of dollars, except share data)	2017		2016
Expense	$	15.9	$	7.1
Number of shares	126,000		—

A summary of the status of the Company’s nonvested relative revenue growth performance shares at December 31, 2017 and 2016 is as follows:



	Number of shares (thousands)		Weighted average grant date fair value
Nonvested at December 31, 2015	—		$	—
Granted	485		$	38.62
Vested	(126	)	$	38.62
Forfeited	(39	)	$	38.62
Nonvested at December 31, 2016	320		$	38.62
Granted	198		$	40.08
Vested	(156	)	$	38.62
Forfeited	(7	)	$	39.20
Nonvested at December 31, 2017	355		$	39.42

Based on the Company’s relative revenue growth in excess of the industry vehicle production, it is possible for none of the awards to vest or for a range up to the 200% of the target shares to vest. As of December 31, 2017, there was $9.3 million of unrecognized compensation expense that will be recognized over a weighted average period of approximately 2 years. The unrecognized amount of compensation expense is based on projected performance as of December 31, 2017.