AKAO 2017 Annual Report

84 As of December 31, 2017 2016 2015 2014 2013 (in thousands) Consolidated Balance Sheet Data: Cash, cash equivalents and short-term investments .... $ 164,791 $ 145,876 $ 58,731 $ 63,679 $ 10,738 Working capital ......................................................... 141,503 140,635 56,800 63,917 8,852 Total assets ................................................................ 197,071 163,925 66,863 70,322 20,758 Notes payable ............................................................ 21,957 25,277 14,536 — 6,687 Convertible preferred stock ....................................... — — — — 132,278 Accumulated deficit................................................... (372,838) (247,220) (175,993) (148,900) (128,724) Total stockholders' equity (deficit)............................ 121,962 106,735 43,159 64,613 (124,576)