"I have been a little bit surprised at the sheer magnitude of the strength," Joshua Spencer, portfolio manager at T. Rowe Price, told CNBC's "Closing Bell" on Monday. "I think it reflects some of the fundamentals we see at these companies. If you look across the board, tech fundamentals have been very good in internet, software and semiconductors, so there's been a good backdrop."
While smaller companies exposed to President Donald Trump's agenda — like defense or infrastructure firms — saw early gains after the election, markets have gradually been moving toward bigger names, said Scott Kessler, equity analyst at CFRA Research.
Kessler said the rally among the biggest tech names is likely a combination of the companies' performance and a sense of overall enthusiasm in the stock market.
"Are they leading because they are big, or are they big because they are leading? I kind of think there's a little of both," Kessler said. He added: "Part of it is these companies executing well, people are excited about what's to come. They allow investors to focus on the megatrends of what a lot of us are doing — virtual or augmented reality, self-driving cars — massive greenfields where companies are making tremendous investments."
Kessler's firm has a "strong buy" or "buy" rating on all of the "big five" except Microsoft, in part driven by the companies' earnings and revenues relative to their share prices.
Apple's has recovered over the past year amid better iPhone sales and "positive catalysts on the horizon," Kessler said, while Microsoft's LinkedIn acquisition and move away from mobile phones may be benefitting the stock. Companies like Google and Facebook are investing aggressively in what's next, Kessler said, as evidenced by Facebook's futuristic F8 conference last week.
Companies like Amazon have also changed the relationship between companies and shareholders, NYU Professor Scott Galloway argued in a talk last week, by emphasizing "fast growth and strong vision" above profits.
"In part because they are big, they can make these kinds of investments," Kessler said. "The other subtext clearly is because they are the biggest, you get a disproportionate amount of passively allocated money, and there are benefits to that as well. ... I think these companies have done well by all accounts. People are encouraged by their results."
Trends like cloud computing, the growth of the internet, the penetration of tech into new areas are "real tangible drivers" that can drive results for the companies, said Spencer of T. Rowe Price. Plus, the technology companies came out of the 2008 financial crisis better than many companies, thanks to consolidation during the dot-com bust, Spencer said.
"I think it is a time to be a bit more selective with your stock-picking," Spencer said. "The round numbers [like 6,000] are interesting of course, but the company by company stock prices are really what drive our performance...The last time [the Nasdaq] hit 5,000, back the tech bubble — coming out of that, I really think it was good for tech to go through that period. It really led to a lot of rationalization and companies being leaner."
— CNBC's Fred Imbert contributed to this report
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