Operating expenses are presented on the face of the statement of comprehensive income using a classification based on the functions “Cost of sales,” “Selling and marketing expenses,” “Administrative expenses” and “Research and development expenses.” Total expenses by function were distributed by nature as follows.

SEK in millions

Jan–Dec 2016

Jan–Dec 2015

Goods and sub-contracting services purchased

-17,441

-18,176

Interconnect and roaming expenses

-7,971

-9,042

Other network expenses

-4,695

-4,949

Change in inventories

-3,470

-3,763

Personnel expenses (see also Note C31)

-12,105

-12,171

Marketing expenses

-4,319

-4,847

Other expenses

-8,456

-9,124

Amortization, depreciation and impairment losses

-11,533

-10,880

Total

-69,991

-72,953

Prior period has been restated to reflect the discovery of certain classification errors between net sales and cost of sales referring to insurance sales in region Europe affecting Goods and sub-contracting services purchased by SEK 71 million. 2015 has also been restated to reflect a new cost classification affecting Interconnect and roaming expenses by SEK 71 million and Goods and sub-contracting services purchased by SEK -71 million. The main components of Other expenses are rent expenses, consultant expenses, IT expenses and energy expenses.

Amortization, depreciation and impairment losses by function were as follows.

SEK in millions

Jan–Dec 2016

Jan–Dec 2015

Cost of sales

-9,959

-9,353

Selling and marketing expenses

-1,019

-1,004

Administrative expenses

-509

-499

Research and development expenses

-47

-23

Total

-11,533

-10,880

Total amortization, depreciation and impairment losses for 2016 amounted to SEK 11,533 million, all allocated to the functions above. For more information on amortization, depreciation and impairment losses see Notes C12 “Goodwill and other intangible assets” and C13 “Property, plant and equipment.” Amortization, depreciation and impairment losses are broken down by reportable segment in Note C5 “Segment information.”