Excerpt: Telecom giant SBC Communications Inc. ... last year reported a stunning $2.2 billion plunge in operating income, and the company's explanation probably seemed arcane to many investors. SBC's number-crunchers, the company said, had lowered the expected return on retirement funds by a mere percentage point. Likewise, they raised their assumption of health-care cost inflation by a single point. And they shaved their estimate of future interest rates by just 0.75 percentage points.