(Loss) / earnings per share
Basic (loss) / earnings per share is calculated by dividing net (loss) / income attributable to equity holders of the parent by the weighted average number of common shares outstanding. Diluted (loss) / earnings per share is calculated by adjusting the net (loss) / income attributable to equity holders of the parent and the weighted average number of common shares used for calculating basic per share for the effects of all potentially dilutive shares. Such dilutive common shares are excluded when the effect would be to reduce a loss per share or increase earnings per share.
In the years ended December 31, 2017, 2016 and 2015, there were potentially dilutive items as a result of our Equity Incentive Plans (see Note 16) and our convertible senior notes due 2019, or the Convertible Notes, (as described in Note 13). Potentially dilutive items related to our Equity Incentive Plans and Convertible Notes were excluded from the composition of diluted earnings per share for the years ended December 31, 2017 and December 31, 2016 because their effect would have been anti-dilutive.
We apply the if-converted method when determining diluted (loss) / earnings per share. This requires the assumption that all potential ordinary shares have been converted into ordinary shares at the beginning of the period or, if not in existence at the beginning of the period, the date of the issue of the financial instrument or the granting of the rights by which they are granted. Under this method, once potential ordinary shares are converted into ordinary shares during the period, the dividends, interest and other expense associated with those potential ordinary shares will no longer be incurred. The effect of conversion, therefore, is to increase income (or reduce losses) attributable to ordinary equity holders as well as the number of shares in issue. Conversion will not be assumed for purposes of computing diluted earnings per share if the effect would be anti-dilutive.
