Net Income Per Share

Basic earnings per share is computed by dividing net income available to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted earnings per share includes the weighted average number of common shares outstanding and the number of equivalent shares which would be issued related to the stock options, unvested restricted stock, and warrants using the treasury method, unless such additional equivalent shares are anti-dilutive.

The following table presents the calculation of basic and diluted net income per share (in thousands, except per share information):



	Year Ended December 31,
	2018		2017		2016
Net income	$	24,559	$	18,581	$	20,459
Basic:
Weighted-average shares of common stock outstanding	32,415		33,016		34,023
Shares used in computing basic net income per share	32,415		33,016		34,023

Effect of dilutive securities:
Restricted stock subject to vesting	672		488		493
Contingently issuable shares (1)	—		—		2
Shares issuable for acquisition consideration (2)	415		562		483
Shares used in computing diluted net income per share	33,502		34,066		35,001

Basic net income per share	$	0.76	$	0.56	$	0.60
Diluted net income per share	$	0.73	$	0.55	$	0.58


(1)	For the year ended December 31, 2016, this represents the shares issued to Zeon Solutions Incorporated and certain related entities (collectively, “Zeon”) pursuant to the Asset Purchase Agreement.

(2)

For the year ended December 31, 2018, this represents the shares held in escrow pursuant to: (i) the Asset Purchase Agreement with BioPharm Systems, Inc. (“BioPharm”); (ii) the Asset Purchase Agreement with Zeon; (iii) the Asset Purchase Agreement with RAS & Associates, LLC (“RAS”); (iv) the Asset Purchase Agreement with Clarity Consulting, Inc. and Truth Labs, LLC (together, “Clarity”); (v) the Asset Purchase Agreement with Southport Services Group, LLC (“Southport”); (vi) the Asset Purchase Agreement with Stone Temple Consulting Corporation (“Stone Temple”); and (vii) the Agreement and Plan of Merger with Elixiter, Inc. (“Elixiter”), as part of the consideration. For the year ended December 31, 2017, this represents the shares held in escrow pursuant to: (i) the Asset Purchase Agreement with BioPharm; (ii) the Asset Purchase Agreement with Zeon; (iii) the Asset Purchase Agreement with The Pup Group, Inc. d/b/a Enlighten (“Enlighten”); (iv) the Asset Purchase Agreement with RAS; and (v) the Asset Purchase Agreement with Clarity, as part of the consideration. For the year ended December 31, 2016, this represents the shares held in escrow pursuant to: (i) the Asset Purchase Agreement with BioPharm; (ii) the Asset Purchase Agreement with Zeon; (iii) the Stock Purchase Agreement for Market Street Solutions, Inc. (“Market Street”); and (iv) the Asset Purchase Agreement with Enlighten, as part of the consideration.

The number of anti-dilutive securities not included in the calculation of diluted net income per share were as follows (in thousands):



	Year Ended December 31,
	2018	2017	2016
Restricted stock subject to vesting	31	88	—
Convertible senior notes	3,823	—	—
Warrants related to the issuance of convertible senior notes	3,823	—	—
Total anti-dilutive securities	7,677	88	—

See Note 12, Long-term Debt for further information on the convertible senior notes and warrants related to the issuance of convertible notes.

Prior to 2018, the Company's Board of Directors authorized the repurchase of up to $135.0 million of Company common stock. On February 20, 2018, the Board of Directors authorized the expansion of the stock repurchase program by authorizing the repurchase of up to an additional $25.0 million of Company common stock and extended the expiration date of the program from December 31, 2018 to December 31, 2019. On August 15, 2018, the Board of Directors authorized an additional $75.0 million, for a total repurchase program of $235.0 million. The program could be suspended or discontinued at any time, based on market, economic, or business conditions. The timing and amount of repurchase transactions will be determined by management based on its evaluation of market conditions, share price, and other factors.

Since the program’s inception on August 11, 2008, we have repurchased approximately $199.4 million (14.7 million shares) of our outstanding common stock through December 31, 2018.