A bumper 2013 for Norway's sovereign wealth fund, which invests surplus oil revenue, has made every Norwegian a virtual millionaire in kroner.

After posting its second best year, Norway's so-called "oil fund" -- the world's largest -- signalled a shift away from fossil fuels, notably over environmental concerns.

The fund's market value rose $200 billion last year to top 5 trillion kroner, according to figures released by the central bank on Friday.

That almost makes every single one of the Nordic country's 5.1 million inhabitants a millionaire in the local currency, at least on paper.

Translated into dollars, it means the fund holds around $165,000 per capita.

Despite its name, the Government Pension Fund of Norway is actually saving to guarantee the continuation of its generous welfare benefits for future generations.

Yngve Slyngstad, the oil fund's chief executive, said 2013 was "a good year" in terms of financial performance.

"2013 saw a return to lower uncertainty in the financial markets but also a weak growth of the world economy," Norway's central bank chairman Oeystein Olsen said.

"Paradoxically, this weak growth and the low interest rates abroad are probably the main reasons for the fund's good results in the last two or three years."

According to the Sovereign Wealth Fund Institute, the Norwegian fund is the largest in the world, followed by a fund owned by the United Arab Emirates.

Started in the 1990s, the fund has shares in 8,213 companies around the world and owns 1.3 percent of global market capitalisation, including 2.5 percent of all European shares.

Due to extremely low interest rates throughout the world, bond investments (37.3 of the portfolio) gave no return, while real estate investments in Europe and the US, turned in 11.8 percent.

- Divesting from fossil fuels? -

The fund's portfolio could be facing changes in the near future however, moving away from the very source of its wealth.

The ruling minority right-wing coalition agreed Friday with two small centre-right ally parties to set up an independent panel of experts to examine the possibility of divesting from oil, natural gas and coal.

It was not clear whether any pull-out would affect all fossil fuel extraction companies or only target those where it is the main activity.

It was also unclear whether power companies would be included.

"It is important to look at this issue from every angle before going ahead with changes," said Svein Flaatten, finance spokesman for the conservative party.

The conclusions of the panel, expected next year, could radically change the fund's portfolio: 8.4 percent of its share investments are placed on oil and gas producers.

What may seem like a paradoxical initiative in a country that draws a quarter of its wealth from fossil fuels is explained by environmental concerns but also motivated by economic interest.

Several financial experts have claimed that the fund is doubly exposed to fossil fuels.

A price drop in the fossil fuel sector would mean less state money poured into the fund and also lower returns on the stock markets.

Last year, the fund's overall share return was significantly higher than the 16.1 percent the fund obtained from shares in oil and gas companies.

In December the opposition Labour Party first sparked a debate on the fund going greener when it proposed selling off its investments in "dirty" coal-based energy.

That would put the Norwegian state in a difficult situation, since it owns a company which extracts coal in the Arctic Svalbard archipelago, where it is an essential part of the local economy.

The fund already started selling stakes in coal and gold businesses due to "acute environment challenges", said Slyngstad, who added that the fund would continue to do so this year.