9. INCOME TAX

The following table provides a reconciliation between income taxes calculated at the statutory federal tax rate and the provision for income taxes reflected in the consolidated statements of comprehensive income for December 31:



Dollars in thousands	2015			2014			2013
Income taxes at federal statutory rate	$	31,310		$	35,117		$	35,785
Increase (decrease):
Current state income tax, net of federal tax benefit	4,195			4,666			4,674
Amortization of investment tax credits	(118		)	(201		)	(271		)
Differences required to be flowed-through by regulatory commissions	2,357			2,357			2,357
Gains on company and trust-owned life insurance	(766		)	(689		)	(864		)
Other, net	(1,225		)	393			24
Total provision for income taxes	$	35,753		$	41,643		$	41,705
Effective tax rate	40.0		%	41.5		%	40.8		%

The decrease in the effective income tax rate for 2015 compared to 2014 was primarily due to the benefits of depletion deductions from gas reserves activity. The increase from 2014 compared to 2013 was primarily the result of a $0.6 million income tax charge in 2014 related to a higher statutory tax rate in Oregon, which required the revaluation of deferred tax balances.

The provision (benefit) for current and deferred income taxes consists of the following at December 31:



In thousands	2015		2014		2013
Current
Federal	$	10,558	$	14,823	$	(62	)
State	61		24		(11		)
	10,619		14,847		(73		)
Deferred
Federal	18,729		18,635		35,109
State	6,405		8,161		6,669
	25,134		26,796		41,778
Total provision for income taxes	$	35,753	$	41,643	$	41,705

The following table summarizes the total provision (benefit) for income taxes for the utility and non-utility business segments for December 31:



In thousands	2015			2014			2013
Utility:
Current	$	15,890		$	24,317		$	(73	)
Deferred	20,834			19,518			38,073
Deferred investment tax credits	(118		)	(201		)	(271		)
	36,606			43,634			37,729
Non-utility business segments:
Current	(5,271		)	(9,470		)	—
Deferred	4,418			7,479			3,976
	(853		)	(1,991		)	3,976
Total provision for income taxes	$	35,753		$	41,643		$	41,705

The following table summarizes the tax effect of significant items comprising our deferred income tax accounts at December 31:



In thousands	2015		2014
Deferred tax liabilities:
Plant and property	$	408,342	$	386,732
Regulatory income tax assets	47,427		51,805
Regulatory liabilities	46,400		55,776
Non-regulated deferred tax liabilities	49,683		48,683
Total	$	551,852	$	542,996
Deferred tax assets:
Pension and postretirement obligations	$	4,666	$	6,537
Alternative minimum tax credit carryforward	16,699		16,788
Loss and credit carryforwards	514		12,657
Total	21,879		35,982
Deferred income tax liabilities, net	529,973		507,014
Deferred investment tax credits	48		166
Deferred income taxes and investment tax credits	$	530,021	$	507,180

Management assesses the available positive and negative evidence to estimate if sufficient taxable income will be generated to utilize the existing deferred tax assets. Based upon this assessment, we have determined we are more likely than not to realize all deferred tax assets recorded as of December 31, 2015.

The Company estimates it has Oregon net operating loss (NOL) carryforwards of $3.9 million at December 31, 2015. The NOL carryforwards will be carried forward to reduce our current tax liability in future years. We anticipate that we will be able to utilize the NOL carryforwards before they begin to expire in 2028. Alternative minimum tax (AMT) credits of $16.7 million, general business credits of $0.3 million, and charitable contribution carryforwards of $2.3 million are also available. The AMT credits do not expire, and we anticipate fully using the general business credits and charitable contribution carryforwards before they begin to expire in 2033 and 2016, respectively.

As a result of certain realization requirements prescribed in the accounting guidance for income taxes, the tax benefit of statutory depletion is recognized no earlier than the year in which the depletion is deductible on the Company’s federal income tax return. Income tax expense was decreased by $0.9 million in 2015 as a result of realizing deferred depletion benefit from 2013 and 2014. This benefit is included in Other in the statutory rate reconciliation table.

Uncertain tax positions are accounted for in accordance with accounting standards that require management’s assessment of the anticipated settlement outcome of material uncertain tax positions taken in a prior year, or planned to be taken in the current year. Until such positions are sustained, we would not recognize the uncertain tax benefits resulting from such positions. No reserves for uncertain tax positions existed as of December 31, 2015, 2014, or 2013.

The Company’s examination by the Internal Revenue Service (IRS) for tax years 2009 through 2011 was completed during the first quarter of 2014. The examination did not result in a material change to the returns as originally filed or previously adjusted for net operating loss carrybacks. The IRS Compliance Assurance Process (CAP) examinations of the 2013 and 2014 tax years were completed in the first and fourth quarters of 2015, respectively. There were no material changes to these returns as filed. The 2015 year is currently under IRS CAP examination. The Company’s 2016 CAP application has been accepted by the IRS. Under the CAP program the Company works with the IRS to identify and resolve material tax matters before the tax return is filed each year. As of December 31, 2015, tax year 2012 remains open for federal examination, and tax years 2012 through 2015 remain open for state examination.