Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2023

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of stock options on the date of grant using the Black-Scholes-Merton model and the assumptions listed below:

	January 2022 Grant			January 2021 Grant			March 2020 Grant
Grant date price per share of stock   option award	$	32.19		$	29.84		$	19.63
Expected dividend yield per share		0.00	%		0.00	%		0.00	%
Expected life in years		6.76			6.64			6.40
Expected volatility		54.50	%		54.80	%		42.85	%
Risk-free interest rate		1.52	%		0.59	%		0.87	%
Grant date fair value per share of option   awards	$	17.58		$	15.79		$	8.42

Summary of Performance Stock Units

The following table shows a summary of the performance stock units as of March 31, 2023:

Performance Period	Minimum Shares		Target Shares		Maximum Shares
Market Condition Units
2021 – 2023		66,968		115,036		163,104
2022 – 2024		17,788		117,937		218,086
2023 – 2025		0		78,411		156,822
Performance Condition Units
2023 – 2025		0		188,238		376,476

Summary of Status and Activity of Non-Vested Stock Units

The following table shows a summary of the status and activity of non-vested stock units for the three months ended March 31, 2023:

	Restricted Stock Units			Performance Stock Units			Total Stock Units			Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2022		524,612			237,032			761,644		$	32.40
Granted		201,640			267,073			468,713		$	30.71
Credited from dividends		3,193			1,594			4,787		$	26.80
Vested		(176,248	)		0			(176,248	)	$	26.44
Forfeited		(13,609	)		(6,077	)		(19,686	)	$	32.50
Non-vested at March 31, 2023		539,588			499,622			1,039,210		$	32.62

Summary of Status and Activity of Stock Options

The following table shows a summary of the status and activity of stock options for the three months ended March 31, 2023:

	Options			Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2022		1,122,136		$	27.05
Exercised		(48,709	)	$	19.01
Expired		(36,397	)	$	42.76
Outstanding at March 31, 2023		1,037,030		$	26.88		4.71	$	10.0
Exercisable at March 31, 2023		875,554		$	26.63		4.10	$	8.9

Schedule of Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized under our LTIP and employee stock purchase plan for the three months ended March 31, 2023 and 2022 is as follows:

	Three Months Ended March 31,
	2023		2022
(Dollars in millions)
Stock-based compensation expense recognized:
Selling, general and administrative expenses	$	4.0	$	3.5
Less related income tax benefit		1.1		1.2
Decrease in net income attributable to Koppers	$	2.9	$	2.3
Intrinsic value of exercised stock options	$	0.7	$	0.0
Cash received from the exercise of stock options	$	0.9	$	0.0

Performance Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of the performance stock unit awards with a market condition on the date of grant using the assumptions listed below:

	January 2023 Grant			January 2022 Grant			January 2021 Grant
Grant date price per share of performance   award	$	29.01		$	32.19		$	29.84
Expected volatility		66.30	%		66.90	%		68.70	%
Risk-free interest rate		4.11	%		1.10	%		0.16	%
Look-back period in years		3.00			3.00			3.00
Grant date fair value per share	$	39.51		$	45.19		$	41.50