Billion-dollar unicorns like Uber and Snapchat are sucking up more investor money than ever, and early-stage startups are finding it tough to raise funds, according to a new report from Seattle-based PitchBook.

Private companies valued at $1 billion or more took in $8.78 billion this quarter, or 39 percent of all venture capital invested. That is the most that’s ever been spent on unicorns and way up from last year, when $4.06 billion went to those companies, or approximately 20 percent of venture capital invested that quarter.

A big round for Uber accounted for 28 percent of all venture capital raised this quarter. In May, the rideshare company closed a $5.6 billion round at a pre-money valuation of $61 billion, according to PitchBook.

Venture capitalists invested more than $22.3 billion across 1,906 completed deals in the second quarter, an 11 percent increase in spending over this time last year, but a 29 percent decrease in the number of deals completed.

“Massive mega rounds for companies like Uber and Snapchat are certainly driving up the level of VC dollars invested in the market, but the mentality amongst VCs has shifted dramatically,” PitchBook founder and CEO John Gabbert said in a statement. “In years past, many investors were in bull market mode, making big bets on all types of companies. But today, VCs are more thoughtful about the types of investments they make. The decline in deal volume overall could be a result of this shift.”

Many investors are passing on early-stage startups in favor of more mature companies. The number of angel investments and seed rounds has dropped drastically in the last year from a combined 1,532 to 990 in the last quarter. Still, investors spent more than $2 billion in these rounds, a similar amount to recent quarters, which “indicates that many angel and seed investors still have plenty of money on hand, they are just increasingly selective about where they put it,” according to the report.

The number of seed deals have been declining steadily for almost two years and this quarter hit a five-year low. In the second quarter, 554 seed deals closed, way down from the 1,098 deals completed at this time two years ago.

If a company gets seed funding, getting to the Series A round is tougher than ever. So far this year, only 1.2 percent of startups that closed seed deals completed Series A rounds. That is the lowest rate on record, according to PitchBook.

The report warns that investors’ cautious approaches could lead to a plateau or further diminish spending in early funding rounds.

“As VC fund sizes get bigger and bigger, there’s a need to write bigger checks,” said Garrett Black, senior analyst at PitchBook Data. “Combined with investors’ caution given the general macro climate, this is pushing VC money into mid-stage and late-stage financings of companies with momentum, while the seed stage is increasingly competitive and the barriers to significant institutional capital remain high. It’s never been more important for startups to focus on nailing product-market fit early, minimizing burn rates, etc., in order to increase their likelihood of receiving funding.”