Item 6. Selected Financial Data

In the fourth quarter of 2017, the Company recorded a one-time additional income tax expense of $658 million, or $1.90 per diluted share, related to the enactment of the United States "Tax Cuts and Jobs Act" (the "Act") on December 22, 2017. The provisions of the Act significantly revised the U.S. corporate income tax rules. The additional tax expense recorded in the fourth quarter of 2017 primarily related to a one-time repatriation tax of $676 million on the deemed repatriation of post-1986 undistributed earnings of foreign subsidiaries and $53 million of additional foreign withholding taxes related to the expected repatriation of foreign held cash and equivalents. These additional tax charges were partially offset by an $82 million one-time income tax benefit related to the remeasurement of deferred tax assets and liabilities in the fourth quarter of 2017 due to the reduction of the U.S. corporate federal tax rate from a maximum of 35% to a flat rate of 21% beginning in 2018 under the Act.

Certain reclassifications of prior year data have been made to conform to current year reporting, including the adoption of new accounting guidance as discussed below.

In March 2016, the Financial Accounting Standards Board (the "FASB") issued authoritative guidance that included several changes to simplify the accounting for stock-based compensation, including the accounting for income taxes, forfeitures, statutory tax withholding requirements and classification of tax benefits in the statement of cash flows. Among the more significant changes, the new guidance requires that the income tax effects associated with the settlement of stock-based awards after adoption of the guidance be recognized through income tax expense rather than directly in equity. Excess tax benefits recognized in equity under the prior guidance were $29 million for the year ended December 31, 2016. The Company adopted the new guidance effective January 1, 2017 and applied the new guidance prospectively. Excess tax benefits of $27 million, $28 million, $10 million and $50 million were included in Income taxes in the statement of income for the years ended December 31, 2020, 2019, 2018 and 2017, respectively. The expected effect on income tax expense or net cash provided from operating activities related to future stock-based award settlements will vary each period and will depend on inputs such as the stock price at the time of settlement and the number of awards settled in the period presented.

Additional information on the comparability of results is included in Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations.