Income statement analysis (Tables)

12 Months Ended

Dec. 31, 2017

Analysis of income and expense [abstract]

Summary of finance income and finance costs

					$ million
	2017		2016		2015
Interest and other income
Interest income	288		183		226
Other income	369		323		385
	657		506		611
Currency exchange losses charged to the income statementa	83		698		8
Expenditure on research and development	391		400		418
Finance costs
Interest payable	1,718		1,221		1,065
Capitalized at 2.25% (2016 1.81% and 2015 1.75%)b	(297	)	(244	)	(179	)
Unwinding of discount on provisions and other payables	653		698		461
	2,074		1,675		1,347

^a  Excludes exchange gains and losses arising on financial instruments measured at fair value through profit or loss.

^b  Tax relief on capitalized interest is approximately $64 million (2016$56 million and 2015$42 million).