Schedule II—Valuation and qualifying accounts

Description	Balance at beginning of period		Additions charged to expenses		Deductions			Other adjustments		Balance at end of period

As of December 31, 2013:
Allowance for doubtful accounts(1)	$	1,484,087	$	326,457	$	(1,640,870	)	$	—	$	169,674
Deferred tax valuation allowance(2)		29,238,264		903,463		(725,263	)		—		29,416,464
As of December 31, 2012:
Allowance for doubtful accounts	$	1,415,638	$	65,623	$	—		$	2,826	$	1,484,087
Deferred tax valuation allowance(3)		26,452,590		2,845,531		(59,857	)		—		29,238,264
As of December 31, 2011:
Allowance for doubtful accounts	$	1,354,694	$	60,944	$	—		$	—	$	1,415,638
Deferred tax valuation allowance(4)		26,326,256		1,218,415		(1,092,081	)		—		26,452,590

(1): For the year ended December 31, 2013, the decrease to the allowance for doubtful accounts is primarily due to the write-off of a previously reserved trade receivable in the amount of $1.3 million.
(2): For the year ended December 31, 2013, the deferred tax valuation allowance was increased by $0.9 million consisting primarily of an increase of $0.4 million due to the Company's net operating losses and an increase of $0.2 million due to stock options and restricted stock. These increases were offset by decreases in bonus of $0.2 million and bad debt of $0.5 million.
(3): For the year ended December 31, 2012, the deferred tax valuation allowance was increased by $2.8 million consisting of an increase of $1.1 million due to the Company's net operating losses, an increase of $0.7 million due to an increase in stock options and salaries and bonuses, and $1.0 million due to a reduction in the deferred tax liability related to depreciation and amortization that resulted in more deferred tax valuation allowance recorded.
(4): For the year ended December 31, 2011, the deferred tax valuation allowance was increased by $1.2 million consisting of an increase of $0.9 million due to the Company's net operating losses and an increase of $0.3 million due to an increase in stock options and salaries and bonuses. For the year ended December 31, 2011, the deferred tax valuation allowance also decreased by $1.1 million, consisting of an increase of $0.9 million in the deferred tax liability related to depreciation and amortization and a reduction in the allowance for doubtful accounts of $0.2 million that resulted in less deferred tax valuation allowance recorded.