7. Income Taxes

For the three months ended September 30, 2018, our income tax benefit was $0.9 million, compared to $4.3 million for the three months ended September 30, 2017. The following table reconciles our income tax expense for the three and nine months ended September 30, 2018, and 2017, to the U.S. federal statutory rates of 21% and 35%, respectively (in thousands).

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017
Statutory tax at 21% and 35%, respectively	$	(1,088	)	$	(4,470	)	$	(5,362	)	$	(9,885	)
State taxes, net of federal impact		137		171				411			366
Share-based compensation tax shortfall		—			8			70			320
Nondeductible compensation		30			—			123			—
Other differences		—			33			5			42
Write-off of deferred tax assets		—			—			—			139,090
Income tax (benefit) provision	$	(921	)	$	(4,258	)	$	(4,753	)	$	129,933

On December 22, 2017, the Tax Cuts and Jobs Act was enacted which, among other things, lowered the U.S. Federal income tax rate applicable to corporations from 35% to 21% and repealed the corporate alternative minimum tax.

The Exchange Transactions triggered a cumulative change in ownership of our common stock by more than 50% under Section 382 of the Internal Revenue Code as of March 22, 2017. This established an annual limitation on the usage of our pre-change NOLs in the future. Accordingly, we recognized a write-off of our deferred tax assets of $139.1 million in the nine months ended September 30, 2017.