Baupost Group, Boston’s largest hedge fund firm, with $26 billion under management, had investment returns averaging 15 percent in 2013, its best year since 2009, according to Institutional Investor’s Alpha report.

Baupost, run by Seth Klarman, returned $4 billion to customers last year, according to a person briefed on the matter. The firm kept a lot of its money in cash last year -- about 40 percent, according to the trade publication, even as the stock market surged. Baupost is known for seeking out unusual and overlooked investments.