Income Taxes

A reconciliation of the U.S. federal statutory tax rate to the Company’s effective income tax rate is as follows:



	Three months ended March 31,
	2018		2017
U.S. federal statutory tax rate	(21.0	)%	(35.0	)%
State income taxes, net of federal benefit	(37.0	)	(2.2	)
Non-U.S. income taxed at different rates	102.0		0.5
Reduction in tax benefit related to stock-based awards	(217.7	)	6.2
Non-deductible expenses	(44.2	)	(0.7	)
Research and development credit	132.1		1.1
Other	(15.1	)	—
Effective income tax rate	(100.9	)%	(30.1	)%

Fluctuations in effective tax rates have historically been impacted by permanent tax differences with no associated income tax impact, changes in state apportionment factors, including the effect on state deferred tax assets and liabilities, and non-U.S. income taxed at different rates.

Comprehensive tax reform legislation enacted in December 2017, commonly referred to as the Tax Cuts and Jobs Acts (“2017 Tax Act”), made significant changes to U.S. federal income tax laws. The 2017 Tax Act, among other things, reduced the corporate income tax rate from 35% to 21%, partially limited the deductibility of business interest expense and net operating losses, provided additional limitations on the deductibility of executive compensation, imposed a one-time tax on unrepatriated earnings from certain foreign subsidiaries, taxed offshore earnings at reduced rates regardless of whether they are repatriated, and allowed the immediate deduction of certain new investments instead of deductions for depreciation expense over time. The Company has not completed its determination of the impacts of the 2017 Tax Act and recorded provisional amounts in its financial statements as of December 31, 2017. The Company has continued to evaluate the 2017 Tax Act and will adjust the provisional amounts as additional information is obtained. The ultimate impact of the 2017 Tax Act may differ from the provisional amounts recorded due to additional information becoming available, changes in interpretation of the 2017 Tax Act, and additional regulatory guidance that may be issued. No adjustments to the provisional amounts were recorded during the three months ended March 31, 2018.

In January 2017, the Internal Revenue Service notified the Company that it will examine the Company’s federal tax returns for the year ended December 31, 2014. No adjustments have been asserted, and management believes that sustained adjustments, if any, would not have a material effect on the Company’s financial position, results of operations, or liquidity.