Corporate America is reporting another earnings season with 84 percent of S&P 500 companies surpassing analysts' earnings-per-share estimates for the third quarter. This beat rate stands above the five-year average of 78 percent.

But the quality of those beats has deteriorated sharply. The margin by which companies are exceeding profit estimates has compressed to just 2.7 percent in aggregate—well below the five-year average of 7.5 percent and the 10-year average of 8 percent. If this holds through the end of the earnings season, it will mark the smallest positive earnings surprise recorded since the fourth quarter of 2022, according to FactSet's November 6 Earnings Insight report.

This distinction matters. Companies are clearing Wall Street's forecasts, but barely. They are not delivering the level of outperformance investors have come to expect, a red flag for multiple expansion.

Despite shrinking surprise margins, third-quarter earnings are tracking 31.4 percent higher year over year, with 88 percent of S&P 500 companies having reported. This indicates a potential third consecutive quarter of growth exceeding 25 percent. Aggregate revenue growth has reached 14.3 percent.

The tension is clear: corporate profits are expanding rapidly, yet companies are delivering smaller beats against increasingly ambitious expectations. This creates downside risk if guidance disappoints.

Wall Street projects 28.4 percent year-over-year profit growth in the fourth quarter. The question for portfolio managers is whether companies can maintain this elevated pace while continuing to exceed estimates at meaningful margins. Simply meeting ambitious forecasts—rather than consistently outperforming them—could compress valuations.

The S&P 500 trades at 17.7 times forward earnings, below its five-year average of 19.8 times. That valuation cushion assumes earnings growth stays robust. Smaller surprise margins leave little room for disappointment; any shortfall in guidance could trigger sharp repricing.

Watch fourth-quarter earnings calls closely. Forward-looking statements will be decisive for stock performance.