| A summarization of the nature of changes in accounting estimates, including changes that occur in interim periods. Changes in accounting estimate have the effect of adjusting the carrying amounts of existing assets or liabilities or altering the subsequent accounting for existing or future assets or liabilities. Changes in accounting estimates are a necessary consequence of assessments, in conjunction with the periodic presentation of financial statements, of the present status and expected future benefits and obligations associated with assets and liabilities. Changes in accounting estimates result from new or better information. Examples of items for which estimates are necessary are uncollectible receivables, inventory obsolescence, service lives and salvage values of depreciable assets, warranty obligations, and regulatory reviews. |