Note 4. Stock-Based Compensation

The Company accounts for all share-based payments in accordance with ASC Topic 718, “Compensation—Stock Compensation”. Stock‑based compensation expense included in operating expenses for the thirteen-week periods ended December 1, 2018 and December 2, 2017 was as follows:


	Thirteen Weeks Ended
	December 1,		December 2,
	2018		2017
Stock options	$	1,205	$	1,194
Restricted share awards		532		902
Restricted stock units		2,365		1,754
Associate Stock Purchase Plan		72		44
Total		4,174		3,894
Deferred income tax benefit		(1,048)		(1,480)
Stock-based compensation expense, net	$	3,126	$	2,414

Stock options

The fair value of each option grant is estimated on the date of grant using the Black‑Scholes option pricing model with the following assumptions:


	Thirteen Weeks Ended
	December 1,		December 2,
	2018		2017
Expected life (in years)	4.0		4.0
Risk-free interest rate	2.98	%	1.87	%
Expected volatility	23.13	%	22.13	%
Expected dividend yield	2.70	%	2.30	%
Weighted-average grant-date fair value	$14.05		$12.25

A summary of the Company’s stock option activity for the thirteen-week period ended December 1, 2018 is as follows:


	Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding on September 1, 2018	1,760	$	72.96
Granted	398		83.21
Exercised	(118)		79.27
Canceled/Forfeited	(2)		79.35
Outstanding on December 1, 2018	2,038	$	74.59	4.8	$	28,534
Exercisable on December 1, 2018	973	$	72.33	3.7	$	15,819

The unrecognized share‑based compensation cost related to stock option expense at December 1, 2018 was $11,887 and will be recognized over a weighted average period of 2.8 years. The total intrinsic value of options exercised, which represents the difference between the exercise price and market value of common stock measured at each individual exercise date, during the thirteen-week periods ended December 1, 2018 and December 2, 2017 was $618 and $577, respectively.

Restricted share awards

A summary of the non‑vested restricted share award (“RSA”) activity under the Company’s 2005 Omnibus Incentive Plan and 2015 Omnibus Incentive Plan for the thirteen-week period ended December 1, 2018 is as follows:


	Shares	Weighted-Average Grant-Date Fair Value
Non-vested restricted share awards at September 1, 2018	63	$	81.98
Granted	—		—
Vested	(38)		82.44
Canceled/Forfeited	—		—
Non-vested restricted share awards at December 1, 2018	25	$	81.27

The fair value of each RSA is the closing stock price on the NYSE of the Company’s Class A common stock on the date of grant. Upon vesting, a portion of the RSA award may be withheld to satisfy the statutory income tax withholding obligation. The remaining RSAs will be settled in shares of the Company’s Class A common stock when vested. The unrecognized share-based compensation cost related to RSAs at December 1, 2018 was $1,364 and will be recognized over a weighted average period of 1.0 years.

Restricted stock units

A summary of the Company’s non-vested Restricted Stock Unit (“RSU”) award activity for the thirteen-week period ended December 1, 2018 is as follows:


	Shares	Weighted-Average Grant-Date Fair Value
Non-vested restricted stock unit awards at September 1, 2018	377	$	73.18
Granted	151		83.21
Vested	(87)		69.66
Canceled/Forfeited	(5)		76.40
Non-vested restricted stock unit awards at December 1, 2018	436	$	77.31

The fair value of each RSU is the closing stock price on the NYSE of the Company’s Class A common stock on the date of grant. Upon vesting, a portion of the RSU award may be withheld to satisfy the statutory income tax withholding obligation. The remaining RSUs will be settled in shares of the Company’s Class A common stock when vested. These awards accrue dividend equivalents on outstanding units (in the form of additional stock units) based on dividends declared on the Company’s Class A common stock and these dividend equivalents convert to unrestricted common stock on the vesting dates of the underlying RSUs. The dividend equivalents are not included in the RSU table above. The unrecognized share-based compensation cost related to the RSUs at December 1, 2018 was $30,924 and is expected to be recognized over a weighted average period of 3.6 years.