The following table presents Income before income taxes by geographic area (in millions of dollars):

Tax Provision. Income taxes are classified as either domestic or foreign based on whether payment is made or due to the United States or a foreign country. Certain income classified as foreign is also subject to domestic income taxes.

	Federal			Foreign			State			Total
Year Ended December 31, 2020
Current	$	6.1		$	(0.4	)	$	(0.6	)	$	5.1
Deferred		(18.8	)		(0.1	)		(2.3	)		(21.2	)
Benefit (expense) applied to decrease (increase) Retained earnings/Other comprehensive income		5.1			(0.1	)		1.1			6.1
Income tax provision	$	(7.6	)	$	(0.6	)	$	(1.8	)	$	(10.0	)
Year Ended December 31, 2019
Current	$	5.7		$	(1.1	)	$	(1.8	)	$	2.8
Deferred		(19.6	)		(0.3	)		(4.5	)		(24.4	)
Benefit (expense) applied to decrease (increase) Retained earnings/Other comprehensive income		2.7			(0.1	)		0.6			3.2
Income tax provision	$	(11.2	)	$	(1.5	)	$	(5.7	)	$	(18.4	)
Year Ended December 31, 2018
Current	$	11.9		$	(1.9	)	$	(1.5	)	$	8.5
Deferred		(34.7	)		0.1			(1.4	)		(36.0	)
Expense applied to increase Retained earnings/ Other comprehensive loss		(0.7	)		—			(0.1	)		(0.8	)
Income tax provision	$	(23.5	)	$	(1.8	)	$	(3.0	)	$	(28.3	)

The following table presents a reconciliation between the provision for income taxes and the amount computed by applying the federal statutory income tax rate to Income before income taxes (in millions of dollars):

	Year Ended December 31,
	2020			2019			2018
Amount of federal income tax provision based on the statutory rate	$	(8.1	)	$	(16.9	)	$	(25.2	)
(Increase) decrease in federal valuation allowances		—			(0.1	)		1.7
Non-deductible compensation expense		(1.1	)		(1.7	)		(0.6	)
Non-deductible benefit (expense)		0.4			0.1			(1.5	)
State income tax provision, net of federal benefit ¹		(1.5	)		(4.5	)		(2.5	)
Research and development credit		0.4			7.7			—
Gross increases for tax positions from current year		—			(0.3	)		—
Gross decreases (increases) for tax positions from prior years		0.4			(2.4	)		—
Foreign income tax expense		(0.4	)		(0.1	)		(0.5	)
Foreign undistributed (earnings) loss		(0.1	)		(0.2	)		0.4
Tax rate change		—			—			(0.1	)
Income tax provision	$	(10.0	)	$	(18.4	)	$	(28.3	)

Deferred 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 amounts used for income tax purposes. The following table presents the components of our net deferred income tax assets (in millions of dollars):

	As of December 31,
	2020			2019
Deferred income tax assets:
Loss and credit carryforwards	$	33.4		$	48.7
Salaried VEBA (see Note 5)		4.8			8.7
Other assets		29.4			30.1
Leased assets		7.3			7.1
Inventories		6.9			9.4
Valuation allowances		(6.4	)		(9.9	)
Total deferred income tax assets		75.4			94.1
Deferred income tax liabilities:
Property, plant and equipment		(80.8	)		(78.5	)
Leased liability		(6.4	)		(6.3	)
Undistributed foreign earnings		(2.1	)		(2.0	)
Total deferred income tax liabilities		(89.3	)		(86.8	)
Net deferred income tax (liabilities) assets ¹	$	(13.9	)	$	7.3

Tax Attributes. At December 31, 2020, we had $94.6 million of NOL carryforwards available to reduce future cash payments for federal income taxes in the United States. H.R.1, commonly referred to as the Tax Cut and Jobs Act, allows net operating losses generated prior to December 31, 2017 (including our NOL carryforwards) to be fully deducted against 100% of taxable income until fully utilized or expired. Our NOL carryforwards expire periodically through 2030.

In addition, we had $8.1 million of federal research and development (“R&D”) credit carryforwards to offset regular federal income tax requirements. Our R&D credit carryforwards expire periodically through 2040.

In assessing the realizability of deferred tax assets, management considers whether it is “more likely than not” that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers taxable income in carryback years, the scheduled reversal of deferred tax liabilities, tax planning strategies and projected future taxable income in making this assessment. Due to uncertainties surrounding the realization of some of our deferred tax assets, primarily including state NOL carryforwards sustained during the prior years and expiring tax benefits, we have a valuation allowance against our deferred tax assets. When recognized, the tax benefits relating to any reversal of this valuation allowance will be recorded as a reduction of income tax expense. There was a decrease in the valuation allowance of $3.5 million in 2020, an increase in the valuation allowance of $1.5 million in 2019 and a decrease in the valuation allowance of $4.6 million in 2018.

The decrease in the valuation allowance for 2020 was primarily due to the expiration of state NOL carryforwards and the related reversal of their valuation allowances. The increase in the valuation allowance for 2019 was primarily due to unutilized state NOL carryforwards and Federal Separate Return Limitation Year losses that were expected to expire. The decrease in the valuation allowance for 2018 was primarily due to the expiration of state NOL carryforwards and the related reversal of their valuation allowances and the expiration of a capital loss carryforward.

Other. We and our subsidiaries file income tax returns in the U.S. federal jurisdiction and various states and foreign jurisdictions.

Our tax returns for certain past years are still subject to examination by taxing authorities and the use of NOL carryforwards in future periods could trigger a review of attributes and other tax matters in years that are not otherwise subject to examination.

In 2018, we made an accounting policy election to treat global intangible low-taxed income (“GILTI”) as a period cost.

We have gross unrecognized benefits relating to uncertain tax positions. The following table presents a reconciliation of changes in the gross unrecognized tax benefits (in millions of dollars):

	Year Ended December 31,
	2020			2019		2018
Gross unrecognized tax benefits at beginning of period	$	4.1		$	1.5	$	1.5
Gross increases for tax positions of current year		0.1			0.3		—
Gross increases for tax positions of prior years		—			2.3		—
Gross decreases for tax positions of prior years		(0.4	)		—		—
Gross unrecognized tax benefits at end of period	$	3.8		$	4.1	$	1.5

If and when the $3.8 million of gross unrecognized tax benefits at December 31, 2020 are recognized, $1.5 million will be reflected in our income tax provision and thus affect the effective tax rate in future periods.

In addition, we recognize interest and penalties related to unrecognized tax benefits in the income tax provision. We had $0.3 million accrued for interest and penalties at both December 31, 2020 and December 31, 2019. Of these amounts, none were considered current and, as such, were included in Long-term liabilities on our Consolidated Balance Sheets as of December 31, 2020 and December 31, 2019. We recognized an increase in interest and penalty of $0.1 million in our tax provision in both 2019 and 2018.

We do not expect our gross unrecognized tax benefits to significantly change within the next 12 months.