Steadily falling profits are causing valuations to jump in the benchmark gauge for American equity.
Analysts tracked by Bloomberg have lowered forecasts by 2.9 percentage points since the end of June and now anticipate profits will contract by 0.6% in the third quarter, putting US large-cap stocks on track for the longest profit slump since the financial crisis.
Forecasts were cut for nine of the 10 main industries, with prospects for energy and industrial companies worsening the most.
The S&P 500 slipped after closing at a record on Friday amid better-than-forecast jobs data, with losses in healthcare and consumer shares offsetting a rally among energy producers as crude oil climbed.
The gauge traded in the narrowest range in three weeks amid volume that was 20% below the 30-day average.
The Dow Jones Industrial Average lost 25.41 points to 18,518.12.
The Nasdaq Composite Index decreased 0.2% after reaching a record for the first time in a year.
Unusual resilience in equity prices and falling earnings have swelled share valuations.
The S&P 500 is trading for 20.5 times reported operating income, the highest multiple since 2009 and one of the richest valuations since the dot-com bubble burst.
Sluggish global growth has sapped earnings power for companies from Caterpillar to Exxon Mobil, with a stronger dollar depressing overseas demand at the same time the American economy generates lackluster expansion.