Exhibit 12

COMPUTATION OF

RATIO OF EARNINGS TO FIXED CHARGES

(in thousands)

	Year Ended December 31,
	2004			2005			2006			2007			2008
Total Interest Cost
Interest Expense	$	17,698		$	12,558		$	17,675		$	15,697		$	6,292
Capitalized Interest		3,004			3,869			2,553			8,336			20,984
Total Interest Cost (fixed charges)		20,702			16,427			20,228			24,033			27,276
Pre-tax Income		(3,803	)		58,981			118,874			148,601			182,220
Interest Expense		17,698			12,558			17,675			15,697			6,292
Earnings		13,895			71,539			136,549			164,298			188,512
Ratio of earnings to fixed charges(1)(2)(3)		—			4.4	x		6.8	x		6.8	x		6.9x

(1) We have authority to issue up to 5,000 shares of preferred stock, par value $.01 per share; however, there are currently no such shares outstanding and we do not have a preferred stock dividend obligation. Therefore, the ratio of earnings to fixed charges and preferred stock dividends is equal to the ratio of earnings to fixed charges and is not disclosed separately.

(2) For the year ended December 31, 2004, earnings were inadequate to cover fixed charges by $6.8 million. If we adjust earnings to exclude the impact of loss on the early extinguishment of debt incurred in the 2004 and 2005 periods reflected above, the ratio of earnings to fixed charges, as so adjusted, would be 1.8x and 4.5x for the years ended December 31, 2004 and 2005, respectively.

(3) Effective January 1, 2009, we adopted FASB Staff Position (FSP) No. APB 14-1, “Accounting for Convertible Debt Instruments That May Be Settled in Cash upon Conversion (Including Partial Cash Settlements).” APB 14-1 requires that the liability and equity components of a convertible debt instrument within the scope of the FSP be accounted for separately so that the entity’s accounting will reflect additional non-cash interest expense to match the nonconvertible debt borrowing rate when interest cost is recognized in subsequent periods. APB 14-1 requires retrospective application to all periods presented. The impact of APB 14-1 will result in a material increase to non-cash interest expense for financial statements covering the periods ended or ending December 31, 2006 through December 31, 2013. Our ratio of earnings to fixed charges would have been 6.3x, 4.7x, and 4.5x for the years ended December 31, 2006, 2007 and 2008, respectively, had APB 14-1 been in effect since the issuance of our convertible senior notes in November 2006. For further information, see page 42 of our 2008 Annual Report on Form 10-K.