S&P 500 Will Likely Report Year-Over-Year Decline in Earnings in Q3

As of October 4, the S&P 500 is expected to report a decline in earnings of -4.1% for the third quarter. What is the likelihood the index will report an actual decline in earnings of -4.1% for the quarter?

Based on the average change in earnings growth due to companies reporting positive earnings surprises during each earnings season, it is likely the index will report a slight year-over-year decline in earnings in Q3.

When companies in the S&P 500 report actual earnings above estimates during an earnings season, the overall earnings growth rate for the index increases because the higher actual EPS numbers replace the lower estimated EPS numbers in the calculation of the growth rate. For example, if a company is projected to report EPS of $1.05 compared to year-ago EPS of $1.00, the company is projected to report earnings growth of 5%. If the company reports actual EPS of $1.10 (a $0.05 upside earnings surprise compared to the estimate), the actual earnings growth for the company for the quarter is now 10%, five percentage points above the estimated growth rate (10% - 5% = 5%).

Over the past five years on average, actual earnings reported by S&P 500 companies have exceeded estimated earnings by 4.9%. During this same period, 72% of companies in the S&P 500 have reported actual EPS above the mean EPS estimate on average. As a result, from the end of the quarter through the end of the earnings season, the earnings growth rate has typically increased by 3.7 percentage points on average (over the past five years) due to the number and magnitude of positive earnings surprises.

If this average increase is applied to the estimated earnings decline at the end of Q3 (September 30) of -3.8%, the actual earnings decline for the quarter would be -0.1% (-3.8% + 3.7% = -0.1%).

If the index does report a year-over-year decline in earnings in Q3, it will mark the first time the index has reported three straight quarters of year-over-year earnings declines since Q4 2015 through Q2 2016.