Income Taxes

The following table provides details of income taxes for the three months ended March 31, 2017 and 2016 (in thousands, except percentages):



	Three months ended
	March 31,
	2017			2016
Loss before provision for income taxes	$	(995	)	$	(3,835	)
Provision for income taxes	46			61
Effective tax rate	(5		)%	(2		)%

The effective tax rate fluctuates based on the amount of pre-tax income or loss generated in the various jurisdictions where we conduct operations and pay income tax. The income tax expense is primarily due to state minimum income taxes that do not benefit from our state net operating loss carryforwards and to income tax in foreign jurisdictions without net operating loss carryforwards.

As of December 31, 2016, MRV had federal, state and foreign net operating loss ("NOL") carryforwards available of $183.3 million, $112.0 million and $100.8 million, respectively. For federal and state income tax purposes, the NOLs are available to offset future taxable income, begin expiring in 2017 and are available through 2036. Certain foreign NOL carryforwards and tax credits are available indefinitely. Under the Internal Revenue Code, if a corporation undergoes an "ownership change," the corporation's ability to use its pre-change NOLs, capital loss carryforwards and other pre-change tax attributes to offset its post-change income may be limited. An ownership change is generally defined as a greater than 50% change in its equity ownership by value over a three-year period. We may experience an ownership change in the future as a result of subsequent shifts in our stock ownership. If we were to trigger an ownership change in the future, our ability to use any NOLs and capital loss carryforwards existing at that time could be limited. As of March 31, 2017, the federal, state and foreign NOLs had a full valuation allowance.

On January 26, 2016, the Company's Board of Directors approved the adoption of a "Rights Plan" in an effort to protect the Company from potential adverse consequences arising under the Internal Revenue Code, such adverse consequences including a significant reduction in the annual utilization of the Company’s net operating loss carryforwards and built-in losses and the impairment or loss of the NOLs and built-in losses prior to their use.