Item 6. Selected Financial Data

The following selected financial data should be read in conjunction with our consolidated financial statements and the notes thereto, and with Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The statement of operations data for the years ended December 31, 2018, 2017 and 2016, and the balance sheet data as of December 31, 2018 and 2017, have been derived from, and should be read in conjunction with, our audited consolidated financial statements and the notes thereto included herein. The statement of operations data for the years ended December 31, 2015 and 2014, and the balance sheet data as of December 31, 2016, 2015 and 2014, is derived from our historical audited consolidated financial statements and the notes thereto which are not included in this Annual Report on Form 10-K. Dollars are in thousands, except per share amounts.

(1) Amounts for the years ended December 31, 2017, 2016, 2015, and 2014 have not been adjusted under the modified retrospective method of adoption of Accounting Standards Codification Topic 606, Revenue from Contracts from Customers ("Topic 606"), and are presented consistent with the prior period amounts reported under ASC 605. Revenue for the year ended December 31, 2018 would have been $415.1 million under ASC 605.

(2) Reflects the impact of increased spending on research and development and selling, general and administrative expenses to support growth.

(3) Includes the favorable impact of a $8.9 million and $1.8 million discrete tax benefit primarily associated with windfalls related to stock-based compensation for restricted stock units ("RSUs") that vested or stock options that were exercised during the years ended December 31, 2018 and 2017, respectively. Includes tax expense of $8.0 million for the year ended December 31, 2017 related to the the enactment of the Tax Cuts and Jobs Act. Refer to Note 10 of the notes to our consolidated financial statements within this Annual Report on Form 10-K.

(4) In May 2018, we sold 4,645,000 shares of our common stock, which included 645,000 shares pursuant to the full exercise of the underwriters' option to purchase additional shares, in an underwritten public offering at a price of $53.00 per share, which resulted in gross proceeds of $246.2 million. Net proceeds after deducting fees, commissions, and other expenses related to the offering were $234.0 million.

(5) In 2016, 2015, and 2014, we used cash and cash equivalents to repurchase approximately $33.7 million, $7.6 million, and $22.4 million, respectively, of our common shares.

(6) We recorded a net increase in stockholders’ equity (retained earnings) of $19.0 million as of January 1, 2018 due to the cumulative impact of adopting Topic 606 on contracts that were not complete as of that date. Refer to Note 2 of the notes to our consolidated financial statements within this Annual Report on Form 10-K for further discussion.