Three Months
Ended March 31,

Year Ended December 31,

2007

2006

2005

2004

2003

2002

Earnings:

Income from continuing operations before
income taxes

$

57,162

$

142,541

$

250,734

$

316,873

$

299,380

$

340,722

Interest expense (excluding capitalized interest)

12,799

56,661

56,604

32,851

19,241

5,079

Portion of rent expense under long-term operating
leases representative of an interest factor

844

3,675

4,799

4,929

2,478

3,058

Total earnings

$

70,805

$

202,877

$

312,137

$

354,653

$

321,099

$

348,859

Fixed charges:

Interest expense (including capitalized interest)

$

12,799

$

57,051

$

57,399

$

33,299

$

19,241

$

5,139

Portion of rent expense under long-term operating
leases representative of an interest factor

844

3,675

4,799

4,929

2,478

3,058

Total fixed charges

$

13,643

$

60,726

$

62,198

$

38,228

$

21,719

$

58,197

Ratio of earnings to fixed charges

5.2

3.3

5.0

9.3

14.8

42.6