Small-cap stocks are quietly outperforming, and the run may continue — for now

The S&P 500 is up 0.5 percent and the Dow is down 0.5 percent since the start of 2018, but the Russell 2000 has risen 2.3 percent. Furthermore, the S&P 500 is still more than 6 percent off its record high, while the Russell 2000 is less than 3 percent from its all-time high. The U.S.-centric case really rests on the U.S. economy picking up pace from 2.5 percent to perhaps 3 percent growth, and so far, you don't really see that in the data," Schlossberg said, specifically pointing to tepid growth across ISM measures and smaller surveys of growth, like the Empire State Manufacturing Survey.