Net Income Per Share

The Company uses the two-class method to calculate earnings per share. The Company has granted restricted stock that contains non-forfeitable rights to dividends on unvested shares. Since these unvested shares are considered participating securities under the two-class method, the Company allocates earnings per share to common stock and participating securities according to dividends declared and participation rights in undistributed earnings.

Diluted net income per common share is computed based on net income divided by the weighted average number of common and potential common shares outstanding. Potential common shares during the respective periods are those related to dilutive stock-based compensation, including long-term stock-based incentive compensation and directors’ accumulated deferred stock compensation, which may be received by the directors in the form of stock or cash. A reconciliation of the average number of common and potential common shares outstanding used in the calculations of basic and diluted net income per share follows ($ in millions, shares in thousands):



	Three Months Ended						Six Months Ended
	June 30, 2017			June 30, 2016			June 30, 2017			June 30, 2016
Numerator (basic and diluted):
Net income	$	22.3		$	26.0		$	36.0		$	47.1
Less: Dividends paid to participating securities	(0.1		)	—			(0.2		)	(0.1		)
Less: Undistributed earnings available to participating securities	(0.1		)	(0.2		)	(0.1		)	(0.2		)
Undistributed and distributed earnings available to common stockholders	$	22.1		$	25.8		$	35.7		$	46.8

Denominator:
Average number of common shares outstanding	30,412.9			30,313.2			30,389.0			30,304.1
Effect of dilutive stock-based compensation	133.8			134.5			128.1			131.1
Average number of common and potential common shares outstanding	30,546.7			30,447.7			30,517.1			30,435.2