Operating Expenses Net Interest Expense Income Taxes Net Income and Net Income Per Share - Omnicom Group Inc. Operating expenses for 2019 compared to 2018 were (in millions): In 2019, net interest expense decreased $25.2 million year-over-year to $184.0 million. In 2019, interest expense on debt decreased $14.7 million to $227.2 million, primarily reflecting a reduction in interest expense from refinancing activity in the third quarter of 2019 at lower interest rates, including the maturity and retirement of the 2019 Notes and the settlement of the outstanding fixed-to-floating interest rate swaps, partially offset by a loss on the partial redemption of the 2020 Notes and the issuance of the Euro Notes (see Note 7 to the consolidated financial statements). Interest income in 2019 increased $3.1 million year-over-year to $60.3 million due to higher cash balances at our treasury centers. Our effective tax rate for 2019 increased slightly year-over-year to 26.0% from 25.6% in 2018. The effective tax rate for 2019 includes a reduction of $10.8 million primarily from the net favorable settlement of uncertain tax positions in the second quarter of 2019. The effective tax rate for 2018 reflects a net increase of $3.9 million related to an increase in income tax expense for an adjustment to the provisional amounts related to the Tax Act, substantially offset by the impact of a lower tax rate on the net gain on disposition of subsidiaries. Net income - Omnicom Group Inc. in 2019 increased, due to the factors described above, $12.7 million, or 1.0%, to $1,339.1 million from $1,326.4 million in 2018. The net gain on disposition of subsidiaries and repositioning charges, after the allocated share of $6.9 million to noncontrolling interests, and the additional income tax expense from the finalization of the provisional 23 Year Ended December 31, 2019 2018 2019 vs. 2018 $ % of Revenue $ % of Revenue $ Change % Change Revenue $ 14,953.7  $ 15,290.2  $ (336.5) (2.2)% Operating Expenses: Salary and service costs: Salary and service costs 6,895.2  46.1 % 7,127.1  46.6 % (231.9) (3.3)% Third-party service costs 4,077.0  27.3 % 4,179.0  27.3 % (102.0) (2.4)% 10,972.2  73.4 % 11,306.1  73.9 % (333.9) (3.0)% Occupancy and other costs 1,221.8  8.2 % 1,309.6  8.6 % (87.8) (6.7)% Net gain on disposition of subsidiaries —  — % (178.4) (1.2)% 178.4  Cost of services 12,194.0  12,437.3  (243.3) Selling, general and administrative expenses 405.9  2.7 % 455.4  3.0 % (49.5) (10.9)% Depreciation and amortization 231.5  1.5 % 264.0  1.7 % (32.5) (12.3)% 12,831.4  85.8 % 13,156.7  86.0 % (325.3) (2.5)% Operating Profit $ 2,122.3  14.2 % $ 2,133.5  14.0 % $ (11.2) (0.5)% Operating expenses in 2019 decreased $325.3 million, or 2.5%, year-over-year, primarily as a result of our disposition activity in 2019 and 2018, and the weakening of substantially all foreign currencies against the U.S. Dollar. Operating expenses for 2018 also included a net reduction of $29.0 million, comprised of a $178.4 million reduction for the impact of the net gain on disposition of subsidiaries, partially offset by an increase in operating expenses of $149.4 million for repositioning charges, which included $73.7 million in salary and service costs for incremental severance and $73.5 million in occupancy and other costs for office lease termination and consolidation. Salary and service costs, which tend to fluctuate with changes in revenue, decreased $333.9 million, or 3.0%, in 2019 compared to 2018 due to our disposition activity in 2019 and 2018, as well as the incremental severance charge of $73.7 million recorded in 2018 that did not affect 2019. Occupancy and other costs, which are less directly linked to changes in revenue than salary and service costs, decreased $87.8 million, or 6.7%, in 2019 compared to 2018 due to our disposition activity in 2019 and 2018, and the office lease termination and consolidation charge of $73.5 million recorded in 2018 that did not affect 2019. Operating margin increased 0.2% to 14.2% year-over-year and EBITA margin increased 0.2% year-over-year to 14.8%. The net decrease in operating expenses of $29.0 million in 2018 related to the net gain on disposition of subsidiaries partially offset by the charges for the repositioning actions, increased both operating margin and EBITA margin for 2018 by 0.2%. Adjusting for the net decrease of $29.0 million in 2018 in operating expenses, Non-GAAP operating margin for 2019 increased to 14.2% from 13.8% in 2018 and adjusted EBITA margin for 2019 increased to 14.8% from 14.4% in 2018. The year-over-year increase primarily reflects a change in the mix of our business during the current period, including the positive effects following the disposition of underperforming businesses in the current and prior year and our repositioning activity in the third quarter of 2018, as well as our ongoing efforts to manage our cost structure and increase the efficiency of the operations of our agencies.