pre_text: 12. Earnings per share How are earnings per share calculated? Basic earnings per share is calculated by dividing the profit after tax attributable to equity shareholders by the weighted average number of shares in issue after deducting the own shares held by employee share ownership trusts and treasury shares. In calculating the diluted earnings per share, share options outstanding and other potential shares have been taken into account where the impact of these is dilutive. Options over 36m shares (2017/18: 23m shares, 2016/17: 27m shares) were excluded from the calculation of the total diluted number of shares as the impact of these is antidilutive. The earnings per share calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests. Profit after tax was £2,159m (2017/18: £2,032m, 2016/17: £1,908m) and profit after tax attributable to non-controlling interests was £3m (2017/18: £4m, 2016/17: £1m). Profit attributable to non-controlling interests is not presented separately in the financial statements as it is not material.
table: Year ended 31 March 2019 2018 2017
table: Basic weighted average number of shares (millions) 9,912 9,911 9,938
table: Dilutive shares from share options (millions) 6 2 27
table: Dilutive shares from executive share awards (millions) 57 48 29
table: Diluted weighted average number of shares (millions) 9,975 9,961 9,994
table: Basic earnings per share 21.8p 20.5p 19.2p
table: Diluted earnings per share 21.6p 20.4p 19.1p
question: Analyse this data from a financial earnings document. What was the change in the Basic weighted average number of shares (millions) from 2018 to 2019?