The Company calculates earnings (loss) per share using the two-class method. The two-class method allocates net income or loss to each class of common stock and participating security according to common dividends declared and participation rights in undistributed earnings. For reporting periods in which a net loss is recorded, net loss is not allocated to participating securities because the holders of such securities bear no contractual obligation to fund or otherwise share in the loss. Participating securities consist of nonvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents

A summary of the information used in the computation of earnings (loss) per common share follows.

	Years Ended December 31,
($ in thousands, except per share data)	2021		2020			2019
Numerator:
Net income (loss) to common shareholders	$	463,215	$	(45,174	)	$	327,380
Net income or dividends allocated to participating securities - basic and diluted		9,134		1,756			5,546
Net income (loss) allocated to common shareholders - basic and diluted	$	454,081	$	(46,930	)	$	321,834
Denominator:
Weighted-average common shares - basic		86,823		86,533			86,488
Dilutive potential common shares		204		—			111
Weighted average common shares - diluted		87,027		86,533			86,599
Earnings (loss) per common share:
Basic	$	5.23	$	(0.54	)	$	3.72
Diluted	$	5.22	$	(0.54	)	$	3.72

Potential common shares consist of stock options, nonvested performance-based awards, and nonvested restricted share awards deferred under the Company’s nonqualified deferred compensation plan. These potential common shares do not enter into the calculation of diluted earnings per share if the impact would be antidilutive, i.e., increase earnings per share or reduce a loss per share. For reporting periods in which a net loss is reported, such as the year ended December 31, 2020, no effect is given to potentially dilutive common shares in the computation of loss per common share as any impact from such shares would be antidilutive. The weighted average of potentially dilutive common shares that were anti-dilutive totaled 1,079 for the year ended December 31, 2021 and 15,815 for the year ended December 31, 2019 and, as such were excluded from the calculation of diluted earnings per common diluted share for the respective periods.

The diluted earnings per share computation for the year ended December 31, 2019 also excludes the impact of the forward contract related to the October 21, 2019 accelerated share repurchase transaction. Based upon the average daily volume weighted-average price of the Company’s common stock at December 31, 2019, the counterparty to the transaction was expected to deliver additional shares for the settlement of the forward contract upon settlement; as such, the impact of the forward contract related to the accelerated share repurchase transaction would have been anti-dilutive to earnings per share.