Yale’s endowment returns are among the highest in the Ivy League thanks to an obscure Boston hedge fund — just one company in a network of bankers, managers and financiers used to enhance Yale’s portfolio performance.

The hedge fund Bracebridge Capital — founded by Nancy Zimmerman, a trustee of Brown University and a close friend of Yale Chief Investment Officer David Swensen — has grown from $5.8 billion in assets to $10.3 billion in just four years. During that same period, Yale’s endowment grew by $6.6 billion, from $19 billion to $25.6 billion. According to endowment experts interviewed, Yale’s financial success is bolstered by the network of business relationships the University’s Investments Office has cultivated for decades under Swensen.

“Yale and its peers have this tremendous network,” said William Jarvis ’77, managing director of the Commonfund Institute, an institutional investment firm. “Individual investors, and investors who cannot do what Yale does, should surrender.”

The relationship between Zimmerman and Swensen dates back to 1994, when Swensen helped stake around $50 million in one of Zimmerman’s companies with the help of hedge fund manager Thomas Steyer ’79. In past interviews with national media outlets, Swensen has commended Zimmerman’s skill at identifying risk. Swensen and Zimmerman are members of a larger network of business allies that include former New Jersey Gov. Jon Corzine and Princeton’s Chief Investment Officer Andrew Golden SOM ’89, one of Swensen’s protégés.

Wick Sloane SOM ’84, a columnist for Inside Higher Ed, said that Yale benefits from Swensen’s close ties with Bracebridge Capital and with Zimmerman.

“The better David Swensen knows the people at the firms, the better choices he will make for Yale,” Sloane said. “An informed customer is the best customer.”

Because Yale supported Zimmerman’s company in its early stages, the University likely gets exclusive deals, said School of Management professor Roger Ibbotson.

“Yale was an early hedge fund investor … before the hedge fund industry was very large. I’m sure they got all kinds of special deals,” Ibbotson said. “I suspect that the friendship [between Zimmerman and Swensen] is more professional than personal.”

With Zimmerman at its helm, Bracebridge is the largest hedge fund in the world run by a woman. According to Bracebridge’s 2015 filing with the U.S. Securities and Exchange Commission, Zimmerman owns most of Bracebridge Capital. Yet Zimmerman is seldom in the public eye, and has been absent from lists of the top female hedge fund managers. For example, a 2015 article in The Hedge Fund Journal — a publication that gathers information on the industry — did not include Zimmerman on a list of top 50 women in hedge funds.

An aura of mystery shrouds Bracebridge; a Feb. 4 Bloomberg Business article calls the company “secretive.” But Sloane said this might be a poor choice of words, since Bracebridge is not keeping secrets so much as it is staying out of the public eye. Sloane speculated that this privacy comes as a product of Bracebridge’s focus on business, rather than a concerted attempt to conceal its activity.

“Bracebridge seems to be going about its business for its investors, which doesn’t requite publicity for the founders,” Sloane said.

But Zimmerman was not always as far from the limelight as she is now. In 2004, Zimmerman’s husband Andrei Shleifer, an economics professor at Harvard, was found in federal court to have conspired to defraud the U.S. government while he led a government-funded Harvard economic reform program in Russia in the 1990s. The scandal concluded with one of Zimmerman’s former companies paying $1.5 million to resolve claims that it had improperly taken government resources from the Harvard project.

Swensen said in the Bloomberg article that after the scandal, the Yale Investments Office scrutinized Zimmerman’s company to see if there were grounds for Yale to divest from the company or sever business ties.

“We took a hard look and found no reason to modify our relationship,” Swensen told Bloomberg.

Swensen, who came to Yale in 1985, has helped increase Yale’s endowment holdings in private equity and hedge funds. While hedge funds tend to focus on generating maximum short-term profits, private equity can be more illiquid and creates long-term wealth. Since 1985, Yale has increased the holdings of private equity in its endowment asset allocations — the amount of money Yale seeks to invest in specific industries each year.

Hedge funds like Bracebridge are unique for their exclusivity: only well-endowed institutions and people with substantial assets can invest in a hedge fund. Recent market changes, such as the devaluation of China’s currency and falling oil prices globally, have not damaged the Boston firm. Last fiscal year, when the hedge fund industry saw only 0.6 percent growth, Bracebridge grew by 2 percent. Sloane said that articles like the one in Bloomberg are important because they shed light on companies that need to be scrutinized. Hedge funds are not regulated by the U.S. Securities and Exchange Commission.

“These fund managers need more, not less, public scrutiny,” Sloane said.

Bracebridge Capital boasts on its website that its staff members speak 21 languages collectively.