pre_text: Cost of Services Cost of services decreased $204 million, or 1.9%, during 2019 compared to 2018, primarily due to lower access costs resulting from a decline in voice connections, as well as lower employee-related costs associated with the lower headcount resulting from the Voluntary Separation Program, offset by an increase in regulatory fees. Cost of Wireless Equipment Cost of wireless equipment increased $173 million, or 3.8%, during 2019 compared to 2018, primarily driven by a shift to higher priced units in the mix of wireless devices sold and an increase in the number of wireless devices sold. Selling, General and Administrative Expense Selling, general and administrative expense increased $499 million, or 6.5%, during 2019 compared to 2018, due to increases in advertising expenses and sales commission expense, which were partially offset by decreases in employee-related costs resulting from the Voluntary Separation Program. The increase in sales commission expense was primarily due to a lower net deferral of commission costs in 2019 as compared to 2018 as a result of the adoption of Topic 606 on January 1, 2018 using a modified retrospective approach. Depreciation and Amortization Expense Depreciation and amortization expense decreased $153 million, or 3.6%, during 2019 compared to 2018, driven by the change in the mix of total Verizon depreciable assets and Business’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  $10,655 $10,859 $(204) (1.9)%
table: Cost of wireless equipment  4,733 4,560 173 3.8
table: Selling, general and administrative expense  8,188 7,689 499 6.5
table: Depreciation and amortization expense  4,105 4,258 (153) (3.6)
table: Total Operating Expenses  $ 27,681 $ 27,366 $ 315 1.2
question: Analyse this data from a financial earnings document. What is the change in Cost of wireless equipment from 2018 to 2019?