Venture-capital investments in Silicon Valley fell almost 20 percent in the first quarter from a year earlier to $4.9 billion, according to an April report from PricewaterhouseCoopers LLP. Chinese buyers -- hit by a slowing economy and government restrictions on how much money can leave the country -- have slowed purchases after they had “really been driving the market,” said Woodson of Alain Pinel.

“We’re probably moving toward normalization,” said Katharine Carroll, vice president at Pacific Union Real Estate in Palo Alto. “Buyers see that they have a few more options. They don’t feel the urgency that they have to decide on something right away and put an offer in. They can kick the tires a little bit more.”

Statewide Slower

The sale of luxury real estate is slowing statewide, with homes costing more than $3 million sitting on the market 52.5 days in the first quarter, compared with 40 days the year before, said Jordan Levine, an economist at the California Association of Realtors in Los Angeles.

In Santa Clara County, home to Palo Alto, there were 13 sales of homes costing more than $5 million in the first quarter, down from 20 a year earlier, he said. In nearby Los Altos, there were six active listings of homes costing more than $5 million on the market for a median of 25.5 days as of May 14, while the 25 listings in Atherton were on the market a median of 100 days, according to John Burns.

“Given that a larger proportion of the $3 million-plus category is purchased with cash, or folks use some of their other assets to make those kinds of purchases, I think they’re more susceptible to stock-market volatility than your entry-level buyer would be,” Levine said. “That’s one of the big drivers of the current slowdown.”

Mid-Range Demand

There’s no let-up in the demand for homes in the $2 million to $3 million range. Realtors say those properties are still generating multiple offers and selling above asking prices because they are still affordable to software engineers. Aggressive hiring at Facebook and Google is propping up the middle segment of the housing market in Silicon Valley, said Ken DeLeon, founder of DeLeon Realty in Palo Alto.

“Palo Alto is at a crossroads, where some homes are doing very well, and some homes are lingering that last year would have sold with multiple offers,” DeLeon said. “When they do sell, it’s when the seller cuts the price below what they would have gotten last year.”

High-end buyers are pickier and are more likely to let a property go, instead of competing with multiple offers and an auction dynamic that led to homes selling well above asking price until very recently, he said.