13)	Income Taxes

The Company’s effective tax rates for the three months ended March 31, 2019 and 2018 were 18.8% and 17.1%, respectively. The effective tax rate for the three months ended March 31, 2019 and the related income tax expense were lower than the U.S. statutory tax rate due to the U.S. deduction for foreign derived intangible income, the federal tax credit for research activities and the geographic mix of income earned by the Company’s international subsidiaries being taxed at rates lower than the U.S. statutory tax rate, offset by the global intangible low-taxed income inclusion, the limitation on the deduction of executive compensation and state income taxes.

The Company’s effective tax rate for the three months ended March 31, 2018 and the related income tax expense were lower than the U.S. statutory tax rate mainly due to the geographic mix of income earned by the Company’s international subsidiaries being taxed at rates lower than the U.S. statutory tax rate, windfall benefits of stock compensation and the deduction for foreign derived intangible income offset by the tax effects from global intangible low-taxed income and state income taxes.

As of March 31, 2019, the total amount of gross unrecognized tax benefits, which excludes interest and penalties, was approximately $40,725. At December 31, 2018, the total amount of gross unrecognized tax benefits, which excludes interest and penalties, was approximately $32,684. The net increase was primarily attributable to the addition of historical gross unrecognized tax benefits for ESI as a result of the ESI Merger during the quarter ended March 31, 2019. As of March 31, 2019, excluding interest and penalties, there were approximately $33,085 of net unrecognized tax benefits that, if recognized, would impact the Company’s effective tax rate.

The Company accrues interest expense, and if applicable, penalties, for any uncertain tax positions. Interest and penalties are classified as a component of income tax expense. As of March 31, 2019 and December 31, 2018, the Company had accrued interest on unrecognized tax benefits of approximately $543 and $568, respectively.

Over the next 12 months it is reasonably possible that the Company may recognize approximately $1,452 of previously net unrecognized tax benefits, excluding interest and penalties, related to various U.S. federal, state and foreign tax positions primarily as a result of the expiration of certain statutes of limitations.

The Company and its subsidiaries are subject to examination by U.S. federal, state and foreign tax authorities. The U.S. Internal Revenue Service commenced an examination of the Company’s U.S. federal income tax filings for tax years 2015 and 2016 during the quarter ended September 30, 2017. This audit was effectively settled during the quarter ended March 31, 2018, and the impact was not material. Also during the quarter ended March 31, 2018, the Company received notification from the U.S. Internal Revenue Service of their intent to audit its U.S. subsidiary, Newport Corporation, for tax year 2015. This audit commenced during the quarter ended June 30, 2018 and there have been no proposed adjustments through March 31, 2019. The U.S. statute of limitations remains open for tax years 2015 through present. The statute of limitations for the Company’s tax filings in other jurisdictions varies between fiscal years 2013 through present. The Company also has certain federal credit carry-forwards and state tax loss and credit carry-forwards that are open to examination for tax years 2000 through the present.