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The Voorhes

If you look at the tech-heavy Nasdaq stock index, it hardly looks like 1999.

Those stocks currently sport price/earnings ratios of around 20. That's a bit higher than the broad market but nowhere near the crazy 100-plus multiples of the dotcom era. Some big tech names almost seem like value stocks, with P/Es in the low teens.

So why are techies like veteran venture capitalist Bill Gurley making noises about a new bubble? “All this stuff … happened in 1999,” he said at a conference, speaking of new companies that drew sky-high valuations before crashing. The difference now is that much of it is happening in the private market.

Silicon Valley has coined a name, “unicorns,” for startups (often, money-losing ones) that aren’t publicly traded yet have pulled in so much private investment that they have a theoretical valuation of at least $1 billion.

Unicorns are supposed to be rare, but they’re a herd now: CB Insights estimates that there are 144 of them. Famous unicorns include the ride-hailing app Uber and social network Pinterest.

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About half of more than 500 tech startup founders surveyed recently by First Round Capital said tech was “in a bubble.” In late 2015, mutual funds at BlackRock and Fidelity, which own slices of private companies, cut by about half their estimated value of some unicorns.

A culling of the unicorns wouldn’t hit Main Street investors directly. But like 2015’s China crash, it could have ripple effects.

Besides the stakes some funds have, college endowments and pension funds have poured money into Silicon Valley. If a run on unicorns hurt institutional investors, the pain might spread to stocks as people try to raise cash. And it could slow economic growth as less investment goes into companies. “This could further weaken already weak productivity growth,” says Mark Zandi, chief economist at Moody’s Analytics.

What to do: If tech insiders are fretting about a bubble, that’s good reason to be extra skeptical about any glamorous tech IPOs that arrive this year. (An object lesson: the online marketplace Etsy, a 2015 IPO that’s down over 60% from its high.)

If the unicorn bubble pops and it roils shares of more-established tech companies — or the market in general — don’t rush to sell. It may even prove a chance to pick up relative bargains. Zandi says the impact of such an episode is likely to be short-lived.

The really economically scary bubbles are those, like the real estate mania, that are fueled by people going deep into debt. That’s not the case here.