KKR (KKR) - Get Report , the $200 billion U.S. private-equity firm, said profit nearly tripled last quarter as stock markets surged by the most in a decade. 

Net income rose to $1.63 billion from $603 million a year earlier, the New York-based company said Tuesday in a press release. Earnings per share based on generally accepted accounting principles were $1.27. A separate metric preferred by KKR executives known as "after-tax distributable earnings per share," which is not derived using generally accepted accounting principles, was 38 cents -- in line with the average estimate of Wall Street analysts. 

Private-equity firms solicit money from big institutional investors such as state pension funds and then use that capital -- supplemented by ample borrowings via loans or junk-bond sales -- to buy portfolio companies and other assets. Many of the investments are private, meaning they don't trade on stock exchanges, but they're still valued every quarter by KKR's executives, and any markups or markdowns often are roughly correlated with big swings in public markets.

The S&P 500 jumped by 13% in the first quarter, the most in nearly a decade. 

KKR's combined first-quarter revenue and investment income more than doubled from a year earlier to $2.52 billion, while operating expenses rose 77% to $728.8 billion. Assets under management increased by 13% to $200 billion.