Stock-Based Compensation (Tables)

Stock-based compensation expense under the Company’s plans was as follows:


	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2020		2019		2020		2019
Stock-based compensation expense	$	13,006	$	13,434	$	26,771	$	26,298
Tax effect on stock-based compensation expense	(3,317)		(3,504)		(6,826)		(6,859)
Net effect on income	$	9,689	$	9,930	$	19,945	$	19,439

The following weighted average assumptions were used to value options granted during the periods indicated:


	Three Months Ended									Six Months Ended
	June 30,									June 30,
	2020			2019			2020			2019
Grant date fair value of options	$	—		$	—		$	—		$	21.55
Volatility	—		%	—		%	—		%	40.0		%
Risk-free interest rate	—		%	—		%	—		%	2.5		%
Dividend yield	—		%	—		%	—		%	—		%
Expected term (in years)	0.0			0.0			0.0			6.5

The following table summarizes option activity under the Company’s plans:

The following is a summary of the activity for unvested restricted stock units and performance stock units granted under the Company’s plans:


	RSUs				PSUs
	Number of Shares	Weighted- Average Grant Date Fair Value per Share		Number of Shares	Weighted- Average Grant Date Fair Value per Share
Outstanding as of December 31, 2019	1,318,870	$	58.88	254,118	$	67.96
Granted	951,428	74.52		67,793	81.42
Vested	(533,088)	56.77		—	—
Forfeited	(103,133)	59.89		(33,010)	64.70
Outstanding as of June 30, 2020	1,634,077	68.61		288,901	71.49