STOCK-BASED COMPENSATION

We have three types of stock-based compensation awards: restricted stock units (RSUs), stock options and company stock awarded as part of our long-term performance plan (LTPP). The following table sets forth the stock-based compensation expense recorded in selling, general and administrative (SG&A) expense (in millions):



	Three months ended August 31,				Nine months ended August 31,
	2018		2017		2018		2017
Stock-based compensation expense	$	5.5	$	4.0	$	21.6	$	18.4

Our 2018 annual grant of stock options and RSUs occurred in the second quarter, similar to the 2017 annual grant. The weighted-average grant-date fair value of an option granted in 2018 was $20.30 and in 2017 was $17.61 as calculated under a lattice pricing model. Substantially all of the options granted vest ratably over a three-year period or upon retirement. The fair values of option grants in the stated periods were computed using the following range of assumptions for our various stock compensation plans:



	2018	2017
Risk-free interest rates	1.7 - 2.9%	0.9 - 2.4%
Dividend yield	2.0%	1.9%
Expected volatility	18.4%	18.7%
Expected lives (in years)	7.6	7.6

The following is a summary of our stock option activity for the nine months ended August 31, 2018 and 2017:



	2018				2017
(shares in millions)	Number of Shares		Weighted- Average Exercise Price		Number of Shares		Weighted- Average Exercise Price
Outstanding at beginning of period	4.8		$	71.91	4.9		$	66.00
Granted	0.4		105.95		0.6		98.07
Exercised	(0.9	)	51.82		(0.6	)	49.50
Outstanding at end of the period	4.3		$	79.31	4.9		$	71.59
Exercisable at end of the period	3.4		$	73.52	3.9		$	65.12

As of August 31, 2018, the intrinsic value (the difference between the exercise price and the market price) for all options outstanding was $194.2 million and for options currently exercisable was $173.9 million. The total intrinsic value of all options exercised during the nine months ended August 31, 2018 and 2017 was $56.9 million and $26.9 million, respectively.

The following is a summary of our RSU activity for the nine months ended August 31, 2018 and 2017:



	2018				2017
(shares in thousands)	Number of Shares		Weighted- Average Grant-Date Fair Value		Number of Shares		Weighted- Average Grant-Date Fair Value
Outstanding at beginning of period	267		$	86.47	267		$	80.08
Granted	201		101.17		130		94.63
Vested	(117	)	88.35		(118	)	80.62
Forfeited	(6	)	95.68		(12	)	90.65
Outstanding at end of period	345		$	94.21	267		$	86.49

The following is a summary of our LTPP activity for the nine months ended August 31, 2018 and 2017:



	2018				2017
(shares in thousands)	Number of Shares		Weighted- Average Grant-Date Fair Value		Number of Shares		Weighted- Average Grant-Date Fair Value
Outstanding at beginning of period	220		$	84.31	201		$	78.10
Granted	86		101.90		78		89.96
Vested	(59	)	74.02		(43	)	69.04
Forfeited	(2	)	96.74		—		—
Outstanding at end of period	245		$	92.87	236		$	83.63