8. Income Taxes

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets (liabilities) as of December 31, 2014 and 2013 are as follows (in thousands):

	December 31
	2014			2013

Net operating loss carryforwards	$	32,103		$	32,253
Net operating loss carryforwards of foreign subsidiaries	374			374
Book over tax depreciation	(54		)	(43		)
Stock-based compensation expense	10			577
Other	125			116
Deferred tax assets	32,558			33,277
Valuation allowance for deferred tax assets	(32,558		)	(33,277		)
Deferred tax assets, net of allowance	$	—		$	—

Deferred tax assets are required to be reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax assets will not be realized. Realization of the future benefits related to the deferred tax assets is dependent on many factors, including the Company’s ability to generate taxable income within the near to medium term. Management has considered these factors in determining the valuation allowance for 2014 and 2013.

The differences between the provision for income taxes and income taxes computed using the federal statutory rate for the years ended December 31, 2014 and 2013 are as follows (in thousands):

	2014			2013

Reconciliation of income tax benefit to statutory rate:
Income tax (benefit) at statutory rate	$	(93	)	$	212
State income taxes, net of federal income tax benefit	49			4
RTP (ISO expense)	508			—
Permanent differences	13			8
True-up prior year NOL	—			(8		)
Change in valuation allowance	(718		)	2,405
Change in state tax rate	241			(2,605		)
Other	—			(16		)
	$	—		$	—

At December 31, 2014, we had federal net operating loss carryforwards of approximately $85.9 million for income tax purposes that begin to expire in 2021 and are subject to the ownership change limitations under Internal Revenue Code Section 382. We also have approximately $6 million of state net operating loss carryforwards that begin to expire in 2017.