pre_text: Operating Expenses Cost of Services Cost of services increased $549 million, or 3.6%, during 2019 compared to 2018, primarily due to increases in rent expense as a result of adding capacity to the networks to support demand as well as an increase due to the adoption of the new lease accounting standard in 2019, increases in costs related to the device protection package offered to our wireless retail postpaid customers, as well as regulatory fees. These increases were partially offset by decreases in employee-related costs primarily due to the Voluntary Separation Program, as well as decreases in access costs and roaming. Cost of Wireless Equipment Cost of wireless equipment decreased $544 million, or 2.9%, during 2019 compared to 2018, primarily as a result of declines in the number of wireless devices sold as a result of an elongation of the handset upgrade cycle. These decrease were partially offset by a shift to higher priced devices in the mix of wireless devices sold. Selling, General and Administrative Expense Selling, general and administrative expense increased $938 million, or 6.0%, during 2019 compared to 2018, primarily due to increases in sales commission and bad debt expense, and an increase in advertising costs. The increase in sales commission expense during 2019 compared to 2018 was primarily due to a lower net deferral of commission costs as a result of the adoption of Topic 606 on January 1, 2018 using a modified retrospective approach. These increases were partially offset by decreases in employee-related costs primarily due to the Voluntary Separation Program. Depreciation and Amortization Expense Depreciation and amortization expense decreased $599 million, or 5.0%, during 2019 compared to 2018, driven by the change in the mix of total Verizon depreciable assets and Consumer’s usage of those assets.
table: (dollars in millions) Increase/ (Decrease)
table: Years Ended December 31, 2019 2018 2019 vs. 2018
table: Cost of services  $15,884 $15,335 $ 549 3.6%
table: Cost of wireless equipment  18,219 18,763 (544) (2.9)
table: Selling, general and administrative expense  16,639 15,701 938 6.0
table: Depreciation and amortization expense  11,353 11,952 (599) (5.0)
table: Total Operating Expenses  $ 62,095 $ 61,751 $ 344 0.6
question: Analyse this data from a financial earnings document. What is the change in Cost of wireless equipment from 2018 to 2019?