We account for income taxes under FASB Accounting Standards Codification 740, Income Taxes (“ASC 740”). We calculate the quarterly tax provision consistent with the guidance provided by ASC 740-270, whereby we forecast the estimated annual effective tax rate and then apply that rate to the year-to-date pre-tax book (loss) income. The effective tax rate may be subject to fluctuations during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective rate, including factors such as the valuation allowances against deferred tax assets, the recognition or de-recognition of tax benefits related to uncertain tax positions, or changes in or the interpretation of tax laws in jurisdictions where the Company conducts business. There is no tax benefit recognized on certain of the net operating losses incurred due to insufficient evidence supporting the Company’s ability to use these losses in the future. The effective tax rates were as follows:

	Three Months Ended March 31,
(In thousands)	2019			2018
Loss from continuing operations before income taxes	$	(6,045	)	$	(24,862	)
Income tax provision	$	(1,932	)	$	(299	)
Effective tax rate		(32.0	%)		(1.2	%)

Our provision for income taxes differs from the tax computed at the U.S. federal statutory income tax rate due primarily to permanent differences, income attributable to foreign jurisdictions taxed at different rates, state taxes, tax credits and certain discrete items. Our effective tax rate for the three months ended March 31, 2019, compared with the prior year comparable period, differs primarily due to higher tax shortfalls associated with stock-based compensation reflected in the provision for the three months ended March 31, 2019 and valuation allowance of $10.7 million recorded in the three months ended March 31, 2018.

In evaluating our ability to recover our deferred tax assets within the jurisdictions from which they arise, we consider all available evidence, including scheduled reversals of deferred tax liabilities, tax-planning strategies, and results of recent operations. In evaluating the objective evidence that historical results provide, we consider three years of cumulative operating income (loss). During the three months ended March 31, 2019, we recorded immaterial impacts for valuation allowances.

Our unrecognized income tax benefits were $20.8 million and $19.8 million as of March 31, 2019 and December 31, 2018, respectively. If any portion of our unrecognized tax benefits is recognized, it could impact our effective tax rate. The tax reserves are reviewed periodically and adjusted in light of changing facts and circumstances, such as progress of tax audits, lapse of applicable statutes of limitations, and changes in tax law.