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, 2015 and 2014 are as follows (in thousands):

	December 31
	2015			2014

Net operating loss carryforwards	$	31,777		$	32,103
Net operating loss carryforwards of foreign subsidiaries	374			374
Book over tax depreciation	(62		)	(54		)
Stock-based compensation expense	25			10
Other	128			125

Deferred tax assets	32,242			32,558
Valuation allowance for deferred tax assets	(32,242		)	(32,558		)

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 2015 and 2014.

The differences between the provision for income taxes and income taxes computed using the federal statutory rate for the years ended December 31, 2015 and 2014 are as follows (in thousands):

	2015			2014

Reconciliation of income tax benefit to statutory rate:
Income benefit at statutory rate	$	(425	)	$	(93	)
State income taxes (benefit), net of federal income tax benefit	(28		)	49
RTP (ISO expense)	116			508
Permanent differences	65			13
Change in valuation allowance	(316		)	(718		)
Change in state tax rate	577			241
Other	11			—

	$	—		$	—

At December 31, 2015, we had federal net operating loss carryforwards of approximately $86.6 million for income tax purposes that begin to expire in 2022 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.