South Korea's state pension fund is expected to post a return of over 7 percent from stock investment this year thanks largely to a jump in top-cap Samsung Electronics Co., a market tracker said Wednesday.

The value of 281 stocks, of which the National Pension Service owns 5 percent or more, was estimated at 91.3 trillion won ($75.5 billion) as of Monday, up 7.5 percent from 84.6 trillion won at the end of last year, according to FnGuide.

Last year, the NPS registered a stock valuation gain of 1.3 trillion won, while chalking up a valuation loss of 4.6 trillion won the previous year.

The bulk of this year's gains came from a surge in Samsung Electronics, the world's largest smartphone maker and flagship of South Korea's leading family-controlled conglomerate Samsung Group.

The nation's largest institutional investor had an 8.38 stake in the tech behemoth, which was worth 21.2 trillion won, as of Thursday, up 6.3 trillion won from the end of 2015.

The state pension operator's good performance comes as it is under criticism for backing Samsung Group's controversial merger of two units last year. Defying strong opposition from overseas investors, Samsung merged then-Samsung C&T Corp. with Cheil Industries Inc.

The NPS, which held an 11.21-percent stake in then-Samsung C&T Corp. and a 4.84-percent stake in Cheil Industries Inc., threw its weight behind Samsung.

The NPS is the world's third-largest pension operator with assets of 520 trillion won under its management. As of end-September this year, the pension operator's investment in listed South Korean firms reached 100.1 trillion won. (Yonhap)