This excerpt taken from the MRO 10-K filed Mar 10, 2005.
Management's Discussion and Analysis of Critical Accounting Estimates
The preparation of financial statements in accordance with generally accepted accounting principles requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at year end and the reported amounts of revenues and expenses during the year. Actual results could differ from the estimates and assumptions used.
Certain accounting estimates are considered to be critical if a) the nature of the estimates and assumptions is material due to the levels of subjectivity and judgment necessary to account for highly uncertain matters or the susceptibility of such matters to change; and b) the impact of the estimates and assumptions on financial condition or operating performance is material.