Selected Financial Data Income Statement Data (1) (In thousands, except per share amounts) (1) Net income for 2013, 2012, 2011, 2010 and 2009 includes stock-based compensation expense of $7.8 million, $8.0 million,  $7.8 million, $7.1 million and $6.4 million, respectively, net of tax, related to stock option awards. See Note 3 of Notes to the  Consolidated Financial Statements. (2) Assumes exercise of dilutive stock options calculated under the treasury method. See Notes 1 and 14 of Notes to Consolidated  Financial Statements. (3) Working capital consists of current assets less current liabilities. At December 31, 2013 2012 2011 2010 2009 Working capital (3) $277,335 $337,979 $329,311 $304,952 $278,044 Total assets $789,898 $883,656 $817,514 $691,974 $564,463 Total debt $46,500 $46,500 $47,000 $48,000 $48,250 Stockholders’ equity $604,606 $692,406 $692,131 $572,322 $452,515 (In thousands) Balance Sheet Data Year Ended December 31, 2013 2012 2011 2010 2009 Sales Carrier Networks Division $500,733 $492,096 $569,579 $476,030 $371,349 Enterprise Networks Division 141,011 128,518 147,650 129,644 112,836 Total sales 641,744 620,614 717,229 605,674 484,185 Cost of sales 332,858 303,971 302,911 246,811 197,223 Gross profit 308,886 316,643 414,318 358,863 286,962 Selling, general and administrative expenses 129,366 134,523 124,879 114,699 99,446 Research and development expenses 131,055 125,951 100,301 90,300 83,285 Operating income 48,465 56,169 189,138 153,864 104,231 Interest and dividend income 7,012 7,657 7,642 6,557 6,933 Interest expense (2,325) (2,347) (2,398) (2,436) (2,430) Net realized investment gain (loss) 8,614 9,550 12,454 11,008 (1,297) Other income (expense), net (911) 183 (694) (804) 131 Gain on bargain purchase of a business — 1,753 — — — Income before provision for income taxes 60,855 72,965 206,142 168,189 107,568 Provision for income taxes (15,061) (25,702) (67,565) (54,200) (33,347) Net income $45,794 $47,263 $138,577 $113,989 $74,221 Year Ended December 31, 2013 2012 2011 2010 2009 Weighted average shares outstanding—basic  59,001 63,259 64,145 62,490 62,459 Weighted average shares outstanding— assuming dilution (2)  59,424 63,774 65,416 63,879 63,356 Earnings per common share—basic  $0.78 $0.75 $2.16 $1.82 $1.19 Earnings per common share—assuming dilution (2)  $0.77 $0.74 $2.12 $1.78 $1.17 Dividends declared and paid per common share  $0.36 $0.36 $0.36 $0.36 $0.36 ADTRAN 2013 Annual Report 16