Share-based payment transactions
Employees (including directors) of the Group receive remuneration in the form of share-based payment transactions, whereby employees render services as consideration for equity instruments ("equity-settled transactions").
The cost of equity-settled transactions with employees is measured by reference to the fair value at the date at which they are granted. The fair value is determined by using the Black-Scholes option pricing model, further details of which are given in note 26.
The cost of equity-settled transactions is recognized, together with a corresponding increase in equity, over the period in which the performance and/or service conditions are fulfilled. The cumulative expense recognized for equity-settled transactions at the end of the each reporting period until the vesting date reflects the extent to which the vesting period has expired and the Group's best estimate of the number of equity instruments that will ultimately vest. The charge or credit to profit or loss for a period represents the movement in the cumulative expense recognized as at the beginning and end of that period.
No expense is recognized for awards that do not ultimately vest for the Group.
No equity-settled award was cancelled or modified during the years ended December 31, 2015, 2016 and 2017.
The dilutive effect of outstanding options is reflected as additional share dilution in the computation of earnings per share.