U.S. equities rose sharply on Tuesday as solid quarterly reports from several large-cap companies rolled through.
The Nasdaq composite jumped about 0.7 percent, sending the index above 6,000 for this first time ever.
"It's certainly a psychological factor," said Jeff Carbone, managing partner of Cornerstone Financial Partners. "It took us many years to get back above 5,000 and now we're at 6,000. But you've got to be careful."
As CNBC reports, he noted that about 40 percent of the index is being driven by five companies: Amazon, Facebook, Netflix, Alphabet and Apple. "If we see a downturn in those names," the index could be in trouble.