The Russell 2000 Index surged more than 20% in the first half of 2026, its best first-half return since 1991, while the S&P 500 gained 9.6%. Historical data shows that when the Russell 2000 outperforms the S&P 500 in the first half, both indexes tend to struggle in the third quarter, with the Russell 2000 averaging a 2.5% loss and the S&P 500 down 1.5% on average. However, the second half as a whole has historically delivered solid returns, with the S&P 500 averaging a 6.45% gain and positive 70% of the time. Analysis of individual stocks over the past decade indicates that the 25 best-performing S&P 500 stocks in the first half went on to average a 19% return in the second half, while the 25 worst performers averaged a 12% return, both outpacing the remaining stocks' average 8% gain.