13. Net Income (Loss) Per Share Data

Basic net income (loss) per common share is calculated by dividing net income (loss) by the weighted average number of common shares outstanding during the period. Diluted net income per common share is computed by dividing net income by the weighted average number of common and dilutive common equivalent shares outstanding during the period. The Company’s potentially dilutive common shares are those that result from dilutive common stock options, non-vested stock relating to restricted stock awards, restricted stock units, deferred stock units and performance shares. Options to purchase common stock as well as unvested restricted stock and performance stock units are considered to be potentially dilutive common shares, but have been excluded from the calculation of diluted net loss per share as their effect is anti-dilutive for the six months ended March 31, 2018 as a result of the net loss incurred for that period. Therefore, diluted net loss per share was the same as basic net loss per share for the six months ended March 31, 2018. The calculation of weighted average diluted shares outstanding excludes outstanding stock options associated with the right to purchase less than 0.1 million shares of common stock for the three months ended March 31, 2018, as their inclusion would have had an antidilutive effect on diluted net income per share.

The calculation of weighted average diluted shares outstanding excludes outstanding stock options associated with the right to purchase 0.5 million and 0.3 million shares of common stock for the three and six months ended March 31, 2017, respectively, as their inclusion would have had an antidilutive effect on diluted net income per share.

The following table sets forth the denominator for the computation of basic and diluted net income (loss) per share (in thousands):

	Three Months Ended				Six Months Ended
	March 31,				March 31,
	2018		2017		2018			2017
Net income (loss) available to common shareholders	$	1,534	$	506	$	(22	)	$	2,806
Basic weighted average shares outstanding		13,102		13,220		13,078			13,207
Dilutive effect of outstanding stock options, non-vested restricted stock, restricted stock units, deferred stock units and performance shares		363		208		—			208
Diluted weighted average shares outstanding		13,465		13,428		13,078			13,415

The Company’s Board of Directors has authorized the repurchase of up to $25.3 million of the Company’s outstanding common stock. This authorization does not have an expiration date.