Exhibit 12

COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES

(in thousands)

	Years Ended December 31,
	2007		2008		2009		2010		2011
EARNINGS:
Income from continuing operations before income tax expense	$	118,980	$	83,464	$	165,895	$	249,024	$	183,158
Add: Fixed charges		11,839		9,431		6,510		6,276		6,586
Earnings as defined	$	130,819	$	92,895	$	172,405	$	255,300	$	189,744
FIXED CHARGES:
Interest expense	$	8,495	$	6,008	$	4,228	$	4,236	$	4,668
Amortization of deferred financing fees		1,523		666		—		—		—
Interest expense as reported		10,018		6,674		4,228		4,236		4,668
Portion of rent expense as interest		1,821		2,757		2,282		2,040		1,918
Fixed charges as defined	$	11,839	$	9,431	$	6,510	$	6,276	$	6,586
Ratio of earnings to fixed charges		11.1x		9.9x		26.5x		40.7x		28.8x

For purposes of computing the ratios of earnings to fixed charges, earnings represent pretax income from continuing operations plus fixed charges. Fixed charges represent interest expense and the portion of rents representative of interest related to continuing operations.