Radian Group Inc. Notes to Consolidated Financial Statements - (Continued) 21. Net (Loss) Income Per Share 265  As a result of our net loss in 2012 and 2010, 5,872,600 and 4,366,342 shares, respectively, of our common stock  equivalents issued under our stock-based compensation plans were not included in the calculation of diluted net loss per share  because they were anti-dilutive. For the year ended  December 31, 2011, 2,490,462 shares of our common stock equivalents  issued under our stock-based compensation plans were not included in the calculation of diluted net income per share as of  such date because they were anti-dilutive.  Basic net (loss) income per share is based on the weighted average number of common shares outstanding, while diluted  net (loss) income per share is based on the weighted average number of common shares outstanding and common stock  equivalents that would arise from the exercise of stock options.  The calculation of the basic and diluted net (loss) income per share was as follows: Year Ended December 31, 2012 2011 2010 (In thousands, except share and per-share amounts) Net (loss) income . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ (451,468 ) $ 302,150 $ (1,805,867 ) Average common shares outstanding . . . . . . . . . . . . . . . . . . . . . . . . 132,533 132,372 114,697 Increase in shares due to potential exercise of common stock equivalents—diluted basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . — 1,491 — Adjusted shares outstanding—diluted . . . . . . . . . . . . . . . . . . . . . . . . 132,533 133,863 114,697 Net (loss) income per share—basic . . . . . . . . . . . . . . . . . . . . . . . . . . $ (3.41 ) $ 2.28 $ (15.74 ) Net (loss) income per share—diluted . . . . . . . . . . . . . . . . . . . . . . . . $ (3.41 ) $ 2.26 $ (15.74 )