The gains, announced in OPEC's Annual Statistical Bulletin on Tuesday, followed a GDP decline of nearly 33 percent in 2009 after oil had plummeted to less than $40 a barrel from the July 2008 all-time high of more than $147.

Improved cash flow is a big advantage for producer countries, especially after they increased social spending this year in response to the Arab Spring unrest across the Middle East and north Africa.

But the economic gains were mostly less significant than the oil price rally, and analysts were unimpressed by continued over-dependency on a single source of revenue.

"Economic growth is not meaningful if the oil price is the only driver," said Bill Farren-Price of Petroleum Policy Intelligence.

As exports climbed 18 percent in value to just over $1 trillion, import costs increased 8 percent to nearly $620 billion. As a result, the current account surplus increased a whopping 79 percent to $206 billion.

In 2010 Brent crude rose by 28 percent to an average of just above $80 a barrel from $62.67 for 2009, according to Reuters data. This year so far, the oil price has averaged $111.70, up 39 percent on 2010.

OPEC's high proportion of difficult-to-refine, heavy crudes sell for less than higher-quality light Brent crude on international markets, and the OPEC basket price tends to be priced around $4 lower than Brent. On Monday, it ended trade at $112.31, compared with above $116 for Brent futures.

At the same time, the price needs of OPEC member countries have risen sharply, analysts say, following announcements of increased social spending on their growing populations as they seek to counter the unrest of the Arab Spring.

Leading exporter Saudi Arabia used to favor an oil price of $70-$80 a barrel but said at the OPEC meeting in June that range belonged to the past without saying what its new preferred price was.

"Even before the Arab Spring, nearly all the oil producers were facing the demands of population growth," said Neil Atkinson of Datamonitor.

OPEC's figures showed a rise in population to nearly 409 million from more than 398 million in 2009, an increase of around 2.6 percent.

Population growth in Saudi Arabia was slightly higher than the overall figure at 2.8 percent, while the nation's collective gross domestic product reached $443 billion, compared with $2.3 trillion in 2010 for the Organization of the Petroleum Exporting Countries as a whole.

That marked an 11.2 percent rise on 2009, almost canceling the 11.6 percent drop from 2008 to 2009.

The size of OPEC's exports has increased as the group has informally strayed from a record output reduction agreed in December 2009 when it was desperate to shore up a collapsing oil market.

It has never formally revised the December 2009 target, although the failure of the group to agree an output change in June meant it was effectively abandoned.

OPEC's proven crude oil reserves rose 12.1 percent in 2010 to 1.19 trillion barrels. OPEC's growth in oil reserves was mainly due to Venezuela, whose holdings climbed to 296.5 billion barrels from 211.2 billion in 2009, the report said. Top OPEC exporter Saudi Arabia's reserves were steady at 264.5 billion barrels.

Iran and Iraq also boosted their reserves last year. Iraq boosted its reserves to 143 billion barrels last year, up 24 percent, the report said.