The Company’s effective tax rates for the three and six months ended June 30, 2019 were 27.2% and 25.3%, respectively. The effective tax rates for the three and six months ended June 30, 2019 and related income tax expense, were higher than the U.S. statutory tax rate primarily due to a correction of an out of period error with respect to deferred tax assets related to limitations on the deduction of executive compensation in the amount of $5,023. This correction, which should have been recorded during the three months ended September 30, 2018, increased the Company’s effective tax rates in the three and six months ended June 30, 2019 by

9.8

% and

7.5

%, respectively. The prior period error and subsequent correction were not material to prior or current interim and annual financial statements. The effective tax rates for these periods were also higher than the U.S. statutory tax rate due to tax effects of the global intangible low taxed income inclusion offset by the deduction for foreign derived intangible income, the benefit from the reinstatement of a capital loss and the utilization of various tax credits.

The Company’s effective tax rates for the three and six months ended June 30, 2018 were

17.3

% and

17.2

%, respectively. The effective tax rates for the three and six months ended June 30, 2018, and 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 of the global intangible low taxed income inclusion and state income taxes.

As of June 30, 2019, the total amount of gross unrecognized tax benefits, which excludes interest and penalties, was approximately

$40,766.

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 June 30, 2019, if these benefits were recognized in a future period, the timing of which is not estimable, the net unrecognized tax benefit of $33,069, excluding interest and penalties, 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 June 30, 2019 and December 31, 2018, the Company had accrued interest on unrecognized tax benefits of approximately

560

and $

568, respectively.

Over the next 12 months it is reasonably possible that the Company may recognize approximately

1,175

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, for tax year 2015. This audit commenced during the quarter ended June 30, 2018 and was effectively settled during the quarter ended June 30, 2019 with a no change result. The U.S. statute of limitations remains open for tax years 2016 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.