(Recasts lede, adds attrition details, portfolio return rates)
By Joyce Lee
SEOUL, Feb 28 (Reuters) - South Korea's National Pension Service (NPS), the world's third-largest pension fund, said on Tuesday it plans to boost the pay of its fund managers through an extra 4.3 billion won ($3.8 million) budget as it fights to staunch a wave of resignations.
The NPS said in a statement that it plans to increase the fund managers' pay to the upper quartile range of the private sector, after its move to a remote city caused a spike in staff resignations.
Previously, NPS fund managers earned about 70 percent of the pay of their private sector counterparts.
The NPS' Investment Management organization, which has 558 trillion won ($493.24 billion) of assets under managements, has moved its headquarters this month to Jeonju, a city 200 km (125 mile) or three-hour trip away from Seoul by high-speed train and taxi.
The NPS said in the statement 30 people quit its Investment Management organization in 2016 - three times the number in 2015 - and 11 more have given notice so far this year.
NPS said in a statement issued by its overseeing health ministry its 2016 provisional return rate was 4.75 percent, compared to a 4.57 percent return rate in 2015.
Its 2016 overseas stocks investments' return rate of 10.1 percent improved compared to a 5.7 percent return in 2015, while 2016 South Korean stocks' 5.6 percent return rate also bettered the 1.7 percent return rate in 2015.
NPS has some 150.8 trillion won, or 27.1 percent of total assets, invested in overseas assets as of the end of 2016. It previously said it plans to increase overseas investment to 35 percent or more of assets by end of 2021.
The fund is projected to build towards a peak of $2.2 trillion in assets by 2043. ($1 = 1,131.1000 won) (Reporting by Joyce Lee; Editing by Shri Navaratnam)