Accounting Standards Codification 260, Earnings Per Share, requires companies to treat unvested share-based payment awards that have non-forfeitable rights to dividends prior to vesting as a separate class of securities in calculating earnings per share. We have granted and expect to continue to grant to certain employees under our restricted stock agreements, grants that contain non-forfeitable rights to dividends. Such grants are considered participating securities. Therefore, we are required to apply the two-class method in calculating earnings per share. The two-class method of computing earnings per share is an earnings allocation formula that determines earnings per share for each class of common stock and participating security according to dividends declared (or accumulated) and participation rights in undistributed earnings. The dilutive effect of participating securities is calculated using the more dilutive of the treasury method or the two-class method.

Basic earnings per common share was computed using the two-class method by dividing basic net earnings attributable to common stockholders by the weighted-average number of common shares outstanding. Diluted earnings per common share was computed using the two-class method by dividing diluted net earnings attributable to common stockholders by the weighted-average number of common shares outstanding plus dilutive common equivalent shares. Dilutive common equivalent shares include all in-the-money outstanding options or other contracts to issue common stock as if they were exercised or converted. Financial instruments that are not in the form of common stock, but when converted into common stock increase earnings per share are anti-dilutive and are not included in the computation of diluted earnings per share.

During the three and six months ended October 31, 2018 and 2017, restricted stock awards of 0.6 million were outstanding, but not included in the computation of diluted earnings per share because they were anti-dilutive.

The following table summarizes basic and diluted earnings per common share attributable to common stockholders:

	Three Months Ended October 31,				Six Months Ended October 31,
	2018		2017		2018		2017
	(in thousands, except per share data)
Net income attributable to Korn/Ferry International	$	46,034	$	36,331	$	7,423	$	65,372
Less: distributed and undistributed earnings to nonvested restricted stockholders		485		402		118		686
Basic net earnings attributable to common stockholders		45,549		35,929		7,305		64,686
Add: undistributed earnings to nonvested restricted stockholders		425		340		—		568
Less: reallocation of undistributed earnings to nonvested restricted stockholders		419		336		—		561
Diluted net earnings attributable to common stockholders	$	45,555	$	35,933	$	7,305	$	64,693

Weighted-average common shares outstanding:
Basic weighted-average number of common shares outstanding		55,461		55,390		55,420		55,592
Effect of dilutive securities:
Restricted stock		767		585		871		645
ESPP		11		1		14		7
Stock Options		—		2		1		8
Diluted weighted-average number of common shares outstanding		56,239		55,978		56,306		56,252

Net earnings per common share:
Basic earnings per share	$	0.82	$	0.65	$	0.13	$	1.16
Diluted earnings per share	$	0.81	$	0.64	$	0.13	$	1.15