In November 2014, the Company’s board of directors authorized a share repurchase program (the “2014 Repurchase Program”), which supersedes and replaces any prior repurchase programs. Under the 2014 Repurchase Program, the Company is authorized to repurchase up to 3 million shares of the Company’s Class B common stock in the aggregate through open market and privately negotiated transactions, at such times and in such amounts as the Company deems appropriate. Repurchases may also be made under a Rule 10b5-1 plan, which would permit shares to be repurchased when the Company might otherwise be precluded from doing so under insider trading laws. The timing and actual number of shares repurchased will depend on a variety of factors including price, corporate and regulatory requirements, capital availability, and other market conditions. The 2014 Repurchase Program does not have an expiration date and may be expanded, limited or terminated at any time without prior notice. During the three months ended March 31, 2022 and 2021, the Company did not repurchase any Class B common stock.

The Company grants stock-based awards, including stock options, restricted stock awards, and restricted stock units. The Company measures stock-based compensation cost at the grant date based on the fair value of the award and recognizes it as expense over the vesting or service period, as applicable, of the stock-based award using the straight-line method. The Company accounts for forfeitures as they occur.

Stock-based compensation expense was included in the following operating expense categories as follows (in thousands):

	Three Months Ended March 31,
	2021		2022
Service costs	$	8	$	34
Sales and marketing		229		191
Product development		97		82
General and administrative		410		388
Total stock-based compensation	$	744	$	695

The Company uses the Black-Scholes option pricing model to estimate the per share fair value of stock option grants with time-based vesting. The Black-Scholes model relies on a number of key assumptions to calculate estimated fair values. For the three months ended March 31, 2021 and 2022 the expected life of each award granted was determined based on historical experience with similar awards, giving consideration to contractual terms, anticipated exercise patterns, vesting schedules and expirations. Expected volatility is based on historical volatility levels of the Company’s Class B common stock and the expected volatility of companies in similar industries that have similar vesting and contractual terms. The risk-free interest rate is based on the implied yield currently available on U.S. Treasury issues with terms approximately equal to the expected life of the option.

The following weighted average assumptions were used in determining the fair value of time-vested stock option grants for the periods presented:

	Three Months Ended March 31,
	2021	2022
Expected life (in years)	4.0 - 6.25	4.0 - 6.25
Risk-free interest rate	0.64%-1.16%	2.41%-2.44%
Expected volatility	50%-56%	51%-60%

Stock option activity during the three months ended March 31, 2022 is summarized as follows:

	Shares (in thousands)			Weighted average exercise price		Weighted average remaining contractual term (in years)
Balance at December 31, 2021		3,601		$	3.43		6.46
Options granted		254			2.56
Options forfeited		(49	)		3.41
Options expired		(122	)		3.38
Options exercised		(2	)		1.66
Balance at March 31, 2022		3,682		$	3.37		6.65

Restricted stock awards and restricted stock unit activity during the three months ended March 31, 2022 is summarized as follows:

	Shares/ Units (in thousands)			Weighted average grant date fair value
Unvested balance at December 31, 2021		1,518		$	2.80
Granted		251			2.55
Vested		(102	)		2.73
Forfeited		(15	)		3.66
Unvested balance at March 31, 2022		1,652		$	2.76