Income tax expense attributable to earnings consisted of the following components:



		Years ended April 30,
		2012		2011		2010
Current tax expense
Federal	$	9,937	$	(6,171)	$	41,632
State		2,345		1,871		4,794
		12,282		(4,300)		46,426
Deferred tax expense		54,442		60,914		18,194
Total income tax provision	$	66,724	$	56,614	$	64,620

The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and deferred tax liabilities were as follows:



		As of April 30,
		2012		2011		2010
Deferred tax assets
Accrued liabilities	$	13,143	$	10,405	$	9,417
Deferred compensation		5,663		5,325		4,941
Other		7,644		5,562		3,759
Total gross deferred tax assets		26,450		21,292		18,117
Deferred tax liabilities
Excess of tax over book
depreciation		(264,757)		(211,415)		(145,433)
Other		(8,955)		(2,550)		(4,496)
Total gross deferred tax
liabilities		(273,712)		(213,965)		(149,929)
Net deferred tax liability	$	(247,262)	$	(192,673)	$	(131,812)

At April 30, 2012, the Company has net operating loss carryforwards for state income tax purposes of approximately $80,756, which are available to offset future taxable income. These net operating losses expire during the years 2017 through 2032.

There was no valuation allowance for deferred tax assets as of April 30, 2012 and 2011. There was no net change in the valuation allowance for the years ended April 30, 2012 and 2011. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion 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 the scheduled reversal of deferred tax liabilities, projected taxable income, and tax planning strategies in making this assessment.

Total reported tax expense applicable to the Company’s continuing operations varies from the tax that would have resulted from applying the statutory U.S. federal income tax rates to income before income taxes.



	Years ended April 30,
	2012	2011	2010
Income taxes at the statutory rates	35.0%	35.0%	35.0%
Federal tax credits	-2.1	-1.2	-0.8
State income taxes, net of federal tax
benefit	2.9	2.9	2.1
Other	0.6	0.7	-0.7
	36.4%	37.4%	35.6%

The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Company had a total of $7,538 and $6,148 in gross unrecognized tax benefits at April 30, 2012 and 2011, respectively. Of this amount, $4,900 represents the amount of unrecognized tax benefits that, if recognized, would impact our effective tax rate. Unrecognized tax benefits were a net increase of $1,390 during the twelve months ended April 30, 2012 due primarily to the expiration of certain statute of limitations offset by a greater increase associated with state income tax filing positions. This had the effect of increasing the effective state tax rate during the fiscal year ending April 30, 2012. These unrecognized tax benefits predominately relate to risks associated with state income tax filing positions and federal tax credits claimed for the Company’s subsidiaries.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:



		2012		2011
Beginning balance	$	6,148	$	5,482
Additions based on tax positions related to current year		2,706		1,982
Additions for tax positions of prior years		142		48
Reductions for tax positions of prior years		(47)		(192)
Reductions due to lapse of applicable statute of limitations		(1,411)		(1,172)
Settlements		-		-
Ending balance	$	7,538	$	6,148

The total net amount of accrued interest and penalties for such unrecognized tax benefits was $249 and $245 at April 30, 2012 and 2011, respectively, and is included in other long-term liabilities. Net interest and penalties included in income tax expense for the twelve month period ended April 30, 2012 was an increase in tax expense of $4 and a decrease of $5 for the year ended April 30, 2011. At this time, the Company’s best estimate of the reasonably possible change in the amount of the gross unrecognized tax benefits is a decrease of $1,370 during the next twelve months mainly due to the expiration of certain statute of limitations. The federal statute of limitations remains open for the years 2009 and forward. Tax years 2008 and forward are subject to audit by state tax authorities depending on open statute of limitations waivers and the tax code of each state.