

	Year Ended December 31,
	2019			2018		2017
	(Thousands of Dollars)
Current:
U.S.	$	3,741		$	4,515	$	3,117
Foreign	1,489			4,658		6,335
Foreign withholding tax	101			192		479
Total current	5,331			9,365		9,931

Deferred:
U.S.	(490		)	1,403		1,468
Foreign	(168		)	394		(1,065		)
Foreign withholding tax	182			246		(397		)
Total deferred	(476		)	2,043		6

Less: amounts reported in discontinued operations	101			1,251		2,164

Income tax expense	$	4,754		$	10,157	$	7,773

The difference between income tax expense recorded in our consolidated statements of (loss) income and income taxes computed by applying the statutory federal income tax rate (21% for 2019 and 2018 and 35% for 2017) to income before income tax expense is due to the fact that the majority of our income is not subject to federal income tax due to our status as a limited partnership. We record a tax provision related to the amount of undistributed earnings of our foreign subsidiaries expected to be repatriated.

The tax effects of significant temporary differences representing deferred income tax assets and liabilities were as follows:



	December 31,
	2019			2018
	(Thousands of Dollars)
Deferred income tax assets:
Net operating losses	$	26,081		$	21,009
Employee benefits	372			362
Environmental and legal reserves	267			239
Allowance for bad debt	—			1,970
Capital loss	3,870			—
Other	328			1,796
Total deferred income tax assets	30,918			25,376
Less: Valuation allowance	(17,743		)	(12,442		)
Net deferred income tax assets	13,175			12,934

Deferred income tax liabilities:
Property, plant and equipment	(25,169		)	(25,128		)
Foreign withholding tax	(433		)	(234		)
Total deferred income tax liabilities	(25,602		)	(25,362		)

Net deferred income tax liability	$	(12,427	)	$	(12,428	)

Reported on the consolidated balance sheets as:
Deferred income tax liability	$	(12,427	)	$	(12,428	)

As of December 31, 2019, our U.S. and foreign corporate operations have net operating loss carryforwards for tax purposes totaling $96.8 million and $19.1 million, respectively, which are subject to various limitations on use and expire in years 2025 through 2037 for U.S. losses and in years 2019 through 2029 for foreign losses. However, U.S. losses generated after December 31, 2017 can be carried forward indefinitely. As of December 31, 2019, our U.S. corporate operations have a capital loss carryforward for tax purposes totaling $18.4 million, which is subject to limitations on use and expires in 2024.

As of December 31, 2019 and 2018, we recorded a valuation allowance of $17.7 million and $12.4 million, respectively, related to our deferred tax assets. We estimate the amount of valuation allowance based upon our expectations of taxable income in the various jurisdictions in which we operate and the period over which we can utilize those future deductions. The valuation allowance reflects uncertainties related to our ability to utilize certain net operating loss carryforwards before they expire. In 2019, there was a $3.7 million increase in the valuation allowance for the U.S. net operating loss and a $1.6 million increase in the foreign net operating loss valuation allowance due to changes in our estimates of the amount of those loss carryforwards that will be realized, based upon future taxable income.

The realization of net deferred income tax assets recorded as of December 31, 2019 is dependent upon our ability to generate future taxable income in the United States. We believe it is more likely than not that the net deferred income tax assets as of December 31, 2019 will be realized, based on expected future taxable income.