16. [Pro forma reporting] In its April 24, 2001 press release announcing its first quarter 2001 results, Amazon.com [AMZN] reported a "pro forma operating loss" of $49 million or 7% of net sales, compared with $99 million, or 17% of net sales in 2000. The pro forma operating loss excludes stock- based compensation costs. amortization of goodwill and other intangibles, and impairment-related and other costs. Discuss the relevance of pro forma operating loss as a percentage of net sales as an indicator of operating performance, profitabil- ity, and valuation.