Morgan Stanley has China's biggest baby formula maker to thank for its strong earnings.

The US bank reported solid fourth-quarter and full year 2019 earnings Thursday, rounding out a strong week for US banks and sending shares nearly 8% higher.

While revenue from bond trading, fixed income trading, and wealth management rose, the bank's investment management division stood out from the rest. Even though it's the smallest business at the bank, it produced $1.4 billion in revenue, nearly double compared to a year earlier, Morgan Stanley said in a press release.

"The increase this quarter and year was primarily due to an underlying investment, IPO, subject to sales restrictions within an Asia private equity fund," chief financial officer Jon Pruzan said on a call with analysts Thursday.

While Pruzan didn't name the public company, Bloomberg identified it as China Feihe, the largest producer of powdered milk in China.

A Morgan Stanley private equity fund in Asia first invested $50 million in the company six years ago, according to Pruzan. That stake grew to a value of nearly $2 billion after China Feihe's public listing in 2019 and performance since, he said.

Morgan Stanley was able to recognize performance fees and gains in the quarter from the stake, Bloomberg reported . That windfall helped drive the investment group's revenue of $670 million.

Morgan Stanley gained roughly 4% year to date through Wednesday's close.

NOW WATCH: A big-money investor in juggernauts like Facebook and Netflix breaks down the '3rd wave' firms that are leading the next round of tech disruption

See Also:

SEE ALSO: Private-equity giant KKR warns WeWork's fiasco is just the start of many more funding struggles for unicorns and spells out 4 areas where it's investing instead