Stock incentive plans (Tables)

12 Months Ended

Dec. 31, 2023

Stock incentive plans [Abstract]

Assumptions Used in Option Valuation Calculations

The table below indicates the key assumptions (on a weighted-average basis) used in the option valuation calculations for options granted in 2023 and 2022 and a discussion of our methodology for developing each of the assumptions used in the valuation model:

	Years ended December 31,
	2023			2022
Expected option term (in years)		7.0			7.1
Expected volatility		55.6	%		51.3	%
Risk-free interest rate		4.2	%		2.2	%
Dividend yield		0.0	%		0.0	%

Stock Option Activity

Equity award activity in the 2005 Equity Incentive Plan and the 2014 Equity Incentive Plan, as amended, is summarized below:

	Stock Options					Restricted Stock Units
	Number of Shares			Average Price*		Number of Units			Average Price**
Outstanding at December 31, 2022		1,355,955		$	9.08		214,286		$	9.28
Granted		309,800			6.91		210,100			7.21
Exercised		(1,875	)		4.25		(58,705	)		9.55
Forfeited		(271,655	)		7.72		(181,145	)		8.34
Expired		(77,750	)		8.90		–			–
Outstanding at December 31, 2023		1,314,475		$	8.82		184,536		$	7.76

* weighted average exercise price per share

** weighted average grant stock price per share

Equity Awards Vested and Expected to Vest

The following summarizes information about equity awards outstanding that are vested and expect to vest and equity awards that are exercisable at December 31, 2023:

	Equity Awards Vested and Expected to Vest								Equity Awards That Are Exercisable
	Awards		Average Price*		Aggregate Intrinsic Value		Remaining Term**		Awards		Average Price*		Aggregate Intrinsic Value		Remaining Term**
Stock Options		1,314,475	$	8.82	$	316		4.0		968,972	$	9.31	$	167		2.2
Restricted stock units		184,536		–		1,288		2.7		–		–		–		–

* weighted average exercise price per share

** weighted-average contractual remaining term in years