19. NET INCOME PER SHARE

Basic income per share excludes dilution and is computed by dividing net income attributable to Huntsman Corporation common stockholders by the weighted average number of shares outstanding during the period. Diluted income per share reflects all potential dilutive common shares outstanding during the period and is computed by dividing net income available to Huntsman Corporation common stockholders by the weighted average number of shares outstanding during the period increased by the number of additional shares that would have been outstanding as dilutive securities.

Basic and diluted income per share is determined using the following information (in millions):

Additional stock‑based awards of 0.6 million and 0.9 million weighted average equivalent shares of stock were outstanding during the three months ended September 30, 2018 and 2017, respectively, and 0.9 million and 1.8 million weighted average equivalent shares of stock were outstanding during the nine months ended September 30, 2018 and 2017, respectively. However, these stock‑based awards were not included in the computation of diluted earnings per share for the three and nine months ended September 30, 2018 and 2017 because the effect would be anti‑dilutive.