One of the hottest topics in local real estate is what will happen to home prices in and around San Francisco if an expected surge in blockbuster initial public offerings takes place.

There has been lots of talk about newly minted millionaires with fistfuls of IPO cash muscling out other buyers in an already challenging market, but there’s been little evidence to test that theory. Until now.

Three new studies that look at previous IPOs found that they do raise home prices somewhat, with the biggest gains coming closest to the headquarters of companies going public.

That could have big implications for San Francisco, which is the epicenter for an expected wave of offerings by tech companies with multibillion-dollar valuations. Lyft confidentially submitted paperwork for an offering in early December, sort of a precursor to an actual filing, the same week that Uber reportedly did the same. Slack Technologies announced it had filed confidentially on Monday. Other San Francisco companies said to be eyeing an offering include Airbnb and Pinterest.

A working paper first presented at an academic conference last month provides the most relevant insight. Entitled “Cash to Spend: IPO Wealth and House Prices,” it looked at 725 IPOs by California companies between 1993 and 2017 and an index of home prices within 1, 5 and 10 miles of each company’s headquarters.

It looked at the price index three months before and after three dates: the date the company filed for the IPO, the IPO date (when it sold shares to the public) and the end of the lockup period, when employees are free to sell their stock. (Most companies prevent employees from selling for a number of months after the IPO.)

It found that after the filing date, average home prices within a 10-mile radius of headquarters rose by 1 percent more than home prices throughout the same county. After the company went public, the index rose an additional 0.8 percent. Surprisingly, there was no additional gain after the lockup expired.

“Our initial guess was that the big effect was going to be at the expiration of lockup,” said Barney Hartman-Glaser, an assistant finance professor at UCLA who co-authored the study. Maybe it didn’t because “the lockup is anticipated. If I’m a seller, and I know that in two months a bunch of people will have a lot more money to spend, why would I accept a lower price two months earlier? I just won’t sell,” he said.

Could that explain the rash of sellers who took their homes off the market or let their listings expire in December? As I reported last week, 2,493 listings across the Bay Area were withdrawn or expired in December, compared with only 1,154 in December 2017, according to analyst Patrick Carlisle of the Compass real estate firm. In San Francisco, those numbers were 305 and 199, respectively. Carlisle said he thinks the jump “had mostly to do with a cooling market with more market uncertainty and fewer sales,” and was not a response to the Lyft and Uber news.

But the study’s authors thought there could be some connection.

Their surprising results about the lockup period also suggest that pre-IPO shareholders “change their housing demand when their wealth changes,” not when their liquidity increases, and that they “can finance their home purchases based on their illiquid wealth,” the authors wrote. “Banks in California may not be very restrictive in originating mortgages to entrepreneurs and workers at startup firms because of their relatively rich experience with this type of consumers.”

The authors did not consider the fact that many employees working for startups in the late stages of the dot-com boom, when many IPOs in their study took place, never really cashed in on IPOs because by the time their lockup period expired, shares in their companies had plummeted. Hartman-Glaser said they might look at that in the future.

The authors, not surprisingly, found that home prices increased more the closer you got to headquarters and that larger IPOs had a bigger impact than smaller ones. They also discovered that younger companies going public had a bigger impact on home prices than older ones of the same size.

“Managers and workers for those young firms tend to live closer” to work than do employees of older companies, said Jiro Yoshida, an associate business professor at Pennsylvania State University and one of the co-authors.

He figured that a company in the youngest quartile by age and the top quartile by amount raised hypothetically could have raised home prices by 3.7 percent within a 10-mile radius of headquarters (versus 1.8 percent for the average).

Hartman-Glaser suspects that the current crop of IPO candidates might have a smaller impact on home prices than those in his study.

“The flow of information from financial markets to real estate has improved,” since the 1980s, he said.

And companies are waiting so long to go public, by the time they actually file for an IPO, the prospect of new millionaire buyers might already be baked into real estate prices. Now, if IPOs from Uber and the rest are bigger than expected, that could cause home prices to rise, he said.

Hartman-Glaser also cautioned that “most of our results are for Silicon Valley, where the housing stock is very different” than San Francisco.

The biggest IPO in their study was Facebook in May 2012, which raised $16 billion.

In a different study released Tuesday, Zillow looked at the impact that blockbuster deal had on home prices in census tracts with a lot of people who government data suggested worked at Facebook in Menlo Park. It determined that between March 2012 and March 2013, home values in these tracts grew 20.9 percent, compared with 16.8 percent for the 13 surrounding counties.

A census tract roughly equates to a neighborhood. Using data from the U.S. Census Bureau, Zillow economist Jeff Tucker pulled out the 10 tracts that had the most probable Facebook employees in 2012. Redwood Shores was tops, with 50. Some tracts in Palo Alto and Menlo Park had around 30 each. As a share of all workers in those tracts, Facebook accounted for only 1 to 1.5 percent of all workers.

Tucker estimated that for every 10 Facebook employees in a census tract, home prices there grew by 1.6 percentage points more than prices in the 13 surrounding counties. Theoretically, the Facebook IPO could have increased prices in Redwood Shores by 8 percent, he said.

Many employees working for companies expected to go public this year are in the first-time home-buyer demographic. If those firms do go public, that could “mean more competition” for other first-time buyers, Tucker said.

After several years of breakneck growth, Bay Area home prices began appreciating at a much slower rate near the end of last year, and even declined in some cases month to month. IPOs, should they materialize, could halt that recent trend, especially in San Francisco.

“Where prices may have slid a bit, it could cause them to level off instead,” Tucker said.

The third study, “Local Economic Spillover Effects of Stock Market,” looked at the broader impact of IPOs on real estate, labor markets, migration and other factors. It studied about 2,400 IPOs nationwide from 1998 to 2015, but excluded those in 1999 and 2000 (the dot-com peak) and 2003 “because of the lack of income data at the ZIP code level.”

It looked at ZIP codes where a company went public and examined home prices in the same county.

It found that two years after the IPO, the price of “expensive” houses in a ZIP code within a 2-mile radius of the IPO headquarters had increased by 0.7 percent more than homes in the surrounding area. These are homes in the top third price-wise. The IPO did not affect the prices of less expensive homes, said co-author Larry Fauver, an associate finance professor at the University of Tennessee, Knoxville.

If you look just at large IPOs, in the top 20 percent by amount raised, the impact was bigger. In those cases, the value of expensive homes increased by 0.9 percent within 2 miles of headquarters or 0.65 percent within 2 to 5 miles. Many of these larger deals were in the Bay Area.

Kathleen Pender is a San Francisco Chronicle columnist. Email: kpender@sfchronicle.com Twitter: @kathpender