The calculation of basic earnings per share considers only weighted average outstanding common shares in the computation. The calculation of diluted earnings per share gives effect to all potentially dilutive stock options. The calculation of diluted earnings per share is based upon the weighted average number of common shares outstanding during the period, plus, if dilutive, the assumed exercise of stock options using the treasury stock method. Weighted average shares outstanding for the three months ended March 31, 2021 and 2020 were as follows:



	For the three months
	ended March 31,
Amounts in thousands	2021		2020
Weighted average common shares, basic		29,576		29,507
Dilutive effect of stock options		—		—
Weighted average common shares, diluted		29,576		29,507

The following stock options are anti-dilutive and have not been included in the weighted average shares outstanding calculation:



	For the three months
	ended March 31,
Amounts in thousands	2021		2020
Stock options		1,022		1,410