5. NET INCOME PER SHARE

On May 1, 2013, pursuant to the Second Modified Fifth Amended Plan of Reorganization of Ambac (the "Reorganization Plan"), 45,000,000 shares of new common stock at par value of $0.01 per share and 5,047,138 of warrants were issued. Warrants entitled such holders to acquire up to 5,047,138 shares of new common stock at an exercise price of $16.67 per share at any time on or prior to April 30, 2023. For the three and six months ended June 30, 2017 and 2016, 0 and 136 warrants were exercised, respectively, resulting in an issuance of 0 and 136 shares of common stock, respectively.

On June 30, 2015, the Board of Directors of Ambac authorized the establishment of a warrant repurchase program that permits the repurchase of up to $10,000 of warrants. For the six months ended June 30, 2017, Ambac repurchased 0 warrants at a cost of $0. As of June 30, 2017, Ambac has repurchased 985,331 warrants totaling $8,092, (average cost of $8.21 per warrant) leaving 4,053,670 warrants outstanding. On November 3, 2016, the Board of Directors of Ambac authorized a $10,000 increase to the warrant repurchase program, bringing the remaining aggregate authorization at June 30, 2017 to $11,939.

Basic net income per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares outstanding and vested restricted stock units. Diluted net income per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares used for basic earnings per share plus all potential dilutive common shares outstanding during the period. All potential dilutive common shares outstanding consider common stock deliverable pursuant to warrants issued under the Reorganization Plan, vested and unvested options, unvested restricted stock units and performance stock units granted under employee and director compensation plans.

The following table provides a reconciliation of the common shares used for basic net income per share to the diluted shares used for diluted net income per share:



	Three Months Ended June 30,		Six Months Ended June 30,
	2017	2016	2017	2016
Basic weighted average shares outstanding	45,369,213	45,212,484	45,330,946	45,194,731
Effect of potential dilutive shares ⁽¹⁾:
Warrants	250,289	—	—	—
Stock options	—	—	—	—
Restricted stock units	27,609	104,457	—	80,680
Performance stock units	126,398	58,147	—	34,132
Diluted weighted average shares outstanding	45,773,509	45,375,088	45,330,946	45,309,543
Anti-dilutive shares excluded from the above reconciliation:
Stock options	126,667	176,668	126,667	176,668
Warrants	—	4,178,901	—	4,178,901
Restricted stock units	—	23,334	68,654	23,334
Performance stock units ⁽²⁾	151,527	—	342,092	—


(1)	For the six months ended June 30, 2017, Ambac had a net loss and accordingly excluded all potentially dilutive securities from the determination of diluted loss per share as their impact was anti-dilutive.


(2)	Performance stock units are reflected herein at their target issuance amounts. Vesting of these units is contingent upon meeting certain performance metrics. Although a portion of these performance metrics have been achieved as of the respective period end, it is possible that awards may no longer meet the metric at the end of the performance period.