Components of earnings before income taxes and noncontrolling interests are as follows (in thousands):

	Year Ended December 31,
	2019			2018		2017
United States	$	1,806,704		$	3,160,111	$	1,610,652
Foreign		(23,897	)		69,280		139,305
	$	1,782,807		$	3,229,391	$	1,749,957

	Year Ended December 31,
	2019			2018			2017
Current:
Federal	$	241,074		$	633,868		$	504,865
State		62,685			96,622			37,308
Foreign		8,981			14,800			48,386
Total current		312,740			745,290			590,559
Deferred:
Federal		101,946			4,953			(207,006	)
State		8,013			6,847			(4,533	)
Foreign		(10,802	)		(8,783	)		(9,634	)
Total deferred		99,157			3,017			(221,173	)
Total provision for income taxes	$	411,897		$	748,307		$	369,386

A reconciliation of the federal statutory tax rate (21% in 2019 and 2018, and 35% in 2017) to the total provision is as follows:

	Year Ended December 31,
	2019	2018	2017
Taxes computed at statutory rate	21.00%	21.00%	35.00%
State income taxes, net of federal income tax benefit	3.16%	2.52%	1.22%
Federal research credit	-0.34%	-0.14%	-0.24%
Domestic manufacturing deduction	—	—	-2.58%
Equity in losses of foreign joint venture	0.19%	0.08%	0.13%
Foreign rate differential	—	-0.07%	-0.62%
Noncontrolling interests	-1.18%	-0.78%	-1.24%
Tax Reform Act	—	0.18%	-10.01%
Other, net	0.27%	0.38%	-0.55%
Provision for income taxes	23.10%	23.17%	21.11%

For the year ended December 31, 2019, the effective tax rate on continuing operations decreased 0.07% versus the prior year to 23.10%. The 2018 effective tax rate included the write-off of $21.3 million (0.66%, included in the Other, net line for 2018) of deferred tax assets due to the change in the tax status of a subsidiary in 2018.

The Tax Reform Act impacted the effective tax rates in both 2018 and 2017. The impacts on the 2018 effective tax rate included the lower federal income tax rate of 21% (35% in 2017), the loss of the domestic manufacturing deduction (-2.58% in 2017) and two SAB 118 adjustments totaling $5.8 million. These SAB 118 adjustments had an impact of 0.18% on the 2018 effective tax rate and are included in the Tax Reform Act line for 2018. The 2017 effective tax rate included a provisional net benefit of $175.2 million (-10.01%) mainly driven by the revaluation of the Company's net U.S. deferred tax assets and liabilities due to the enactment of the Tax Reform Act.

	December 31,
	2019			2018
Deferred tax assets:
Accrued liabilities and reserves	$	146,658		$	128,553
Allowance for doubtful accounts		18,479			20,134
Inventory		79,363			63,950
Post-retirement benefits		10,288			8,746
Commodity hedges		5,164			1,393
Net operating loss carryforward		59,083			27,131
Tax credit carryforwards		164,132			16,792
Other deferred tax assets		8,508			779
Valuation allowance		(192,295	)		(30,104	)
Total deferred tax assets		299,380			237,374
Deferred tax liabilities:
Holdbacks and amounts not due under contracts		(12,930	)		(10,731	)
Intangibles		(171,531	)		(167,374	)
Property, plant and equipment		(545,890	)		(390,575	)
Total deferred tax liabilities		(730,351	)		(568,680	)
Total net deferred tax liabilities	$	(430,971	)	$	(331,306	)

Tax credit carryforwards were $164.1 million at December 31, 2019 ($16.8 million at December 31, 2018). The increase in the balance was primarily due to state tax credits in the amount of $147.3 million that were awarded in 2019. Nucor believes utilization of these credits is unlikely. For this reason, the

Company has also established a corresponding valuation allowance for $147.3 million. The remaining movement in valuation allowance is primarily driven by state and foreign net operating losses generated in the current year for which Nucor believes utilization is unlikely.

Non-current deferred tax assets included in other assets were $0.0 million at December 31, 2019 ($0.7 million at December 31, 2018). Non-current deferred tax liabilities included in deferred credits and other liabilities were $431.0 million at December 31, 2019 ($332.0 million at December 31, 2018). Current federal and state income taxes receivable included in other current assets were $240.8 million at December 31, 2019 ($26.2 million at December 31, 2018). Nucor paid $525.2 million in net federal, state and foreign income taxes in 2019 ($561.1 million in 2018 and $699.8 million in 2017).

Nucor has not recognized deferred tax liabilities on its investment in foreign subsidiaries with undistributed earnings that satisfy the permanent reinvestment requirements (the deferred tax liabilities on the investments not permanently reinvested are immaterial). While Nucor considers future earnings to be permanently reinvested, it is expected that potential future distributions will likely be of a nontaxable manner. If this assertion of permanent reinvestment were to change there may be deferred tax liabilities related to the withholding tax impacts on the actual distribution of certain cumulative undistributed foreign earnings, but the Company believes this amount to be immaterial.

State net operating loss carryforwards were $681.8 million at December 31, 2019 ($483.0 million at December 31, 2018). If unused, they will expire between 2020 and 2039. Foreign net operating loss carryforwards were $149.8 million at December 31, 2019 ($58.6 million at December 31, 2018), of which $19.5 million have no expiration. If unused, the remaining $130.3 million of foreign loss carryforwards will expire between 2025 and 2039.

At December 31, 2019, Nucor had approximately $50.9 million of unrecognized tax benefits, of which $50.2 million would affect Nucor's effective tax rate, if recognized. At December 31, 2018, Nucor had approximately $48.6 million of unrecognized tax benefits, of which $48.0 million would affect Nucor's effective tax rate, if recognized.

A reconciliation of the beginning and ending amounts of unrecognized tax benefits recorded in deferred credits and other liabilities is as follows (in thousands):

	December 31,
	2019			2018			2017
Balance at beginning of year	$	48,605		$	48,845		$	44,088
Additions based on tax positions related to current year		9,272			16,424			11,154
Reductions based on tax positions related to current year		—			—			—
Additions based on tax positions related to prior years		2,106			199			2,556
Reductions based on tax positions related to prior years		(2,863	)		(8,198	)		(5,461	)
Reductions due to settlements with taxing authorities		(1,514	)		(2,160	)		—
Reductions due to statute of limitations lapse		(4,686	)		(6,505	)		(3,492	)
Balance at end of year	$	50,920		$	48,605		$	48,845

We estimate that in the next 12 months, our gross uncertain tax positions, exclusive of interest, could decrease by as much as $7.3 million, as a result of the expiration of the statute of limitations.

During 2019, Nucor recognized $0.7 million of expense in interest and penalties ($4.0 million of benefit in 2018 and $2.2 million of benefit in 2017). The interest and penalties are included in interest expense, net and marketing, administrative and other expenses, respectively, in the consolidated statements of earnings. As of December 31, 2019, Nucor had approximately $11.9 million of accrued interest and penalties related to uncertain tax positions (approximately $11.2 million at December 31,

2018). The accrued interest and penalties are included in accrued expenses and other current liabilities and deferred credits and other liabilities, respectively, on the consolidated balance sheets.

Nucor has concluded U.S. federal income tax matters for years through 2014. The tax years 2015 through 2018 remain open to examination by the Internal Revenue Service. The Canada Revenue Agency has concluded its examination of the 2012 and 2013 Canadian returns for Harris Steel Group Inc. and certain related affiliates. The 2015 tax year is currently under examination by the Canada Revenue Agency. The Trinidad and Tobago Inland Revenue Division has concluded its examination of the Nu-Iron Unlimited 2013 corporate income tax return. The tax years 2013 through 2018 remain open to examination by other major taxing jurisdictions to which Nucor is subject (primarily Canada and other state and local jurisdictions).