Table:
|  | 2019 €m | 2018 €m | 2017 €m |
| --- | --- | --- | --- |
| Continuing (loss)/profit before tax as shown in the consolidated income statement | (2,613) | 3,878 | 2,792 |
| Aggregated expected income tax (credit)/expense | (457) | 985 | 795 |
| Impairment losses with no tax effect | 807 | – | – |
| Disposal of Group investments | – | 55 | (271) |
| Effect of taxation of associates and joint ventures, reported within profit before tax | 262 | 90 | 23 |
| (Recognition)/derecognition of deferred tax assets for losses in Luxembourg and Spain1 | 1,186 | (1,583) | 1,603 |
| Deferred tax following revaluation of investments in Luxembourg1 | (488) | (330) | (329) |
| Previously unrecognised temporary differences we expect to use in the future | – | – | (15) |
| Previously unrecognised temporary differences utilised in the year | – | (29) | (11) |
| Current year temporary differences (including losses) that we currently do not expect to use | 78 | 20 | 139 |
| Adjustments in respect of prior year tax liabilities2 | (94) | (244) | (107) |
| Revaluation of assets for tax purposes | – | – | (39) |
| Impact of tax credits and irrecoverable taxes | 79 | 93 | 98 |
| Deferred tax on overseas earnings3 | (39) | 24 | 26 |
| Effect of current year changes in statutory tax rates on deferred tax balances | (2) | (44) | 2,755 |
| Financing costs not deductible for tax purposes | 67 | 23 | 25 |
| Expenses not deductible (income not taxable) for tax purposes | 97 | 61 | 72 |
| Income tax expense/(credit) | 1,496 | (879) | 4,764 |
Paragraphs:
Factors affecting the tax expense for the year
The table below explains the differences between the expected tax expense, being the aggregate of the Group’s geographical split of profits multiplied by the relevant local tax rates and the Group’s total tax expense for each year.
Notes: 1 See note below regarding deferred tax asset recognition in Luxembourg and Spain on pages 140 and 141
2 2018 includes the impact of closing tax audits across the Group during the year, including in Germany and Romania
3 Includes a €42 million credit (2018: €15 million charge, 2017 €95 million charge) relating to the combination of Vodafone India with Idea Cellular
Question:
What is the change between 2017-2018 and 2018-2019 average income tax expense?
Answer: [1496 +(-879)]/ 2 - [(-879)+ 4764]/ 2 = -1634