(Reuters) - Underwhelming performances of Snap and Blue Apron since their high-profile market debuts, especially at a time when the U.S. stock market is hitting record highs, is an indication that the IPO market will not be as robust as expected this year.

The logo of Blue Apron is shown on screens above the floor of the New York Stock Exchange before the company's IPO in New York, U.S., June 29, 2017. REUTERS/Lucas Jackson

Snap Inc SNAP.N, owner of the popular photo-messaging app Snapchat, and meal-kit delivery company Blue Apron Holdings Inc APRN.N are trading well below the prices they listed at earlier this year.

And though the U.S. IPO market has already raked in more money so far this year than it did in all of 2016, the underperformance of these stocks has sensitized investors to valuations and made them cautious about putting money on the table, IPO experts said.

“Second half of 2017 will be better than 2016, but we might not get to the 2015, 2014 levels this year,” said Kathleen Smith, principal of Renaissance Capital LLC, a manager of IPO-focused exchange-traded funds.

This puts a damper on an IPO market that was largely expected to make a strong comeback after a poor 2016, especially for technology companies that typically bring in the highest proceeds.

Richard Truesdell, co-head of global capital markets at law firm Davis Polk & Wardwell, said there were worries that over-valuation would lead to fewer tech IPOs and more conservative valuations this year than originally predicted.

A star-studded lineup of companies including ride-hailing company Uber Technologies Inc [UBER.UL], home-sharing company Airbnb and music streaming service Spotify were expected to make their debuts in 2017, but are yet to file with regulators.

Uber, valued over $60 billion, has other problems as well. The company, beset by complaints about its workplace culture, is also facing a federal inquiry and has been sued by Waymo, the self-driving car unit of Google parent Alphabet Inc GOOGL.O.

Snap currently trades about 15 percent below its IPO price of $17, while Blue Apron is down about 35 percent from its IPO price of $10.

Snap in May reported slowing user growth and revenue in its first quarter after its IPO. Blue Apron is yet to report results after going public.

A strong after-debut performance often rests on a company’s profitability and Snap and Blue Apron’s lack of profits in the face of stiff competition from deep-pocketed rivals have raised questions about their ability to turn around.

There’s hope yet.

A few bright spots in the IPO market, including big-data analytics company Cloudera Inc's CLDR.N debut, could help boost investor enthusiasm as long as valuations rationalize over the next couple of months.

Cloudera joins a small group of companies whose stocks have done well after their listings, including Canadian apparel maker Canada Goose Holdings Inc GOOS.TOGOOS.N and flooring retailer Floor & Decor Holdings Inc FND.N.

The Renaissance IPO ETF is up 25 percent this year, far outperforming the 9 percent increase in the S&P 500 index .SPX.

Several private companies are expected to seek public listing in the second half of 2017, according to Renaissance Capital. Genealogy website Ancestry.com and buyout firm Thoma Bravo-backed Riverbed Technology are among them.