14. INCOME TAXES

Income or (loss) before income taxes for the years ended December 31, 2016, 2015 and 2014 is summarized as follows (in thousands):

	Year Ended December 31,
	2016			2015			2014
United States	$	(21,753	)	$	(13,707	)	$	(719	)
Foreign		(19,609	)		—			—
	$	(41,362	)	$	(13,707	)	$	(719	)

The components of the provision for (benefit from) income taxes are summarized as follows (in thousands):

	As of December 31,
	2016			2015		2014
Current
Federal	$	49		$	—	$	—
State		11			—		—
Foreign		32			—		—
Total Current		92			—		—
Deferred
Federal		(251	)		—		(1,500	)
State		(49	)		—		—
Foreign		(1,398	)		—		—
Total Deferred		(1,698	)		—		(1,500	)
Provision for (benefit from) income taxes	$	(1,606	)	$	—	$	(1,500	)

The Company’s actual provision for tax differed from the amounts computed by applying the U.S. federal income tax rate of 34% to pretax income as a result of the following:

	Year Ended December, 31,
	2016			2015			2014
Federal tax at statutory rate		34.0	%		34.0	%		34.0	%
Stock-based compensation		-0.5	%		-1.9	%		-9.5	%
Change in valuation allowance		-16.8	%		-31.1	%		190.6	%
Foreign rate differential		-1.3	%		0.0	%		0.0	%
Preferred stock warrant revaluation		-0.2	%		0.0	%		-0.7	%
Interest expense		0.0	%		0.0	%		-5.8	%
Contingent liability for IMX acquisition		0.4	%		0.0	%		38.2	%
Acquisition costs		-1.2	%		-3.2	%		-36.7	%
Goodwill impairment		-10.8	%		0.0	%		0.0	%
Other		0.3	%		2.2	%		-1.3	%
Effective income tax rate		3.9	%		0.0	%		208.8	%

Deferred income tax assets and liabilities consist of the following: (in thousands):

	As of December 31,
	2016			2015
Deferred tax assets:
Net operating loss carryforwards	$	71,925		$	65,957
Tax credit carryforwards		4,947			4,533
Accruals		1,274			1,125
Other		1,088			698
Gross deferred tax assets		79,234			72,313
Valuation allowance		(76,295	)		(70,053	)
Total deferred tax assets		2,939			2,260

Deferred tax liabilities:
Property and equipment		195			95
Purchased intangibles		(8,979	)		(2,355	)
Other		(212	)		—
Total deferred tax liabilities		(8,996	)		(2,260	)
Net deferred tax liabilities	$	(6,057	)	$	—

The Company assesses the realizability of its net deferred tax assets by evaluating all available evidence, both positive and negative, including (1) cumulative results of operations in recent years, (2) sources of recent losses, (3) estimates of future taxable income and (4) the length of net operating loss carryforward periods. The Company believes that based on the history of its U.S. losses and other factors, the weight of available evidence indicates that it is more likely than not that it will not be able to realize its U.S. net deferred tax assets. Accordingly, the U.S. net deferred tax assets have been offset by a full valuation allowance. The valuation allowance increased by $6.2 million and $3.7 million during the years ended December 31, 2016 and 2015, respectively.

As of December 31, 2016, the Company had domestic federal net operating loss carryforwards of $198.2 million, domestic state net operating loss carryforwards of $102.1 million, and foreign net operating loss carryforwards of $2.4 million that can reduce future taxable income. The domestic federal and state net operating loss carryforwards will begin to expire in 2018 and 2017, respectively. The foreign net operating loss carryforwards can be carried forward indefinitely.

As of December 31, 2016, the Company had credit carryforwards of approximately $3.9 million and $4.8 million available to reduce future taxable income, if any, for domestic federal and California state income tax purposes, respectively. The domestic federal credit carryforwards begin to expire in 2021. California credits have no expiration date.

Utilization of the Company's net operating loss and credit carryforwards may be subject to a substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code of 1986, as amended and similar state provisions. Based on a preliminary review of the Company's equity transactions since inception, the Company believes a portion of its net operating loss carryforwards and credit carryforwards may be limited due to equity financings which occurred in 2000, 2004, 2007, 2014 through the current period.

A reconciliation of the Company’s unrecognized tax benefits is as follows (in thousands):

	Year Ended December 31,
	2016		2015		2014
Balance at beginning of year	$	2,431	$	2,054	$	2,196
Additions based on tax positions related to current year		2,489		372		83
Additions (reductions) based on tax positions related to prior years		332		5		(225	)
Balance at end of year	$	5,252	$	2,431	$	2,054

Approximately $2.6 million of the $5.3 million of unrecognized tax benefit as of December 31, 2016, if recognized, would impact the Company's effective tax rate. During the year ended December 31, 2015, given the Company's valuation allowance, the uncertain tax benefits would not impact the effective tax rate.

The Company recognizes interest and penalties related to unrecognized tax benefits as a component of income tax expense. During the year ended December 31, 2016, the Company recognized $0.3 million of accrued interest and penalties related to unrecognized tax benefits. There were no accruals of interest expense during the years ended December 31, 2015, and 2014. The Company does not anticipate a significant change in the unrecognized tax benefits over the next twelve months.

The Company files U.S., state and foreign income tax returns in jurisdictions with varying statutes of limitations. Due to net operating loss and credit carryovers, the domestic federal and state income tax returns are subject to tax authority examination from inception. In the foreign jurisdictions where the Company files income tax returns, the statutes of limitations with respect to these jurisdictions vary from jurisdiction to jurisdiction and range from 4 to 6 years.