, extending the bull market past the 10-year mark. The tech-heavy Nasdaq Composite reached a record high as well.
There are a couple of reasons that concerns them. One is that a big chunk of the market's recent gains comes from just a few companies. That includes tech giants Microsoft, Apple, Amazon and Alphabet. They've all done far better than the broader stock market, which is up"It suggests there is less participation in the rally," Paul Hickey, the head portfolio manager for the wealth management business of, told Business Insider in an interview.
Another problem is that the last time stocks set records in this narrow way, the market ran into trouble almost immediately. Willie Delwiche, investment strategist for Robert W. Baird, says that in August and September, participation was just as narrow — and in the months after that, the index plunged almost 20%.
"The number of stocks making new highs last summer remained relatively subdued," he said."It becomes kind of a red flag."