Norway's sovereign wealth fund, the world's biggest, posted a negative return of 171 billion kroner (17.7 billion euros, $21.3 billion) in the first quarter, impacted by volatile global stock markets, Norway's central bank said Friday.

While 2017 was the most profitable in its 20-year history, the fund went into 2018 with a negative return of 1.5 percent and saw its value shrink to 8.12 trillion kroner at the end of March.

Tasked with managing the country's oil wealth and intended to finance Norway's generous welfare state when its oil and gas wells run dry, the fund saw a poor showing in its share portfolio, which fell by 2.2 percent. Stocks account for 66.2 percent of the fund's investments.

“The quarter was colored by increased volatility in global stock markets,” the bank said.

The main declines in the quarter were observed in Europe — which fell by three percent, including four percent in Britain — and in North America, which dipped by 2.3 percent.

Bonds, which account for 31.2 percent of the fund's holdings, posted a negative return of 0.4 percent, while real estate investments, which make up 2.7 percent of the portfolio, rose by 2.5 percent.

The fund also shrank because of the government's withdrawal of 11 billion kroner to balance its budget, and negative currency effects of 183 billion kroner.