One museum a day

Last year was exceptionally strong in the US, with $4.8 billion being spent at auctions, an increase of 21 percent from the previous year.

British auction houses also put in a solid performance to secure third place with $2.8 billion in sales, up 35 percent from 2013.

"Demand is constant and aggressive on every continent...notably from museums," says Ehrmann.

"More museums were created between 2000 and 2015 than during the entire 19th and 20th centuries," adds Wang Jie, president of Artprice.com and Artron group.

The phenomenal expansion saw a new museum opening every day somewhere in the world, led by growth in Asia, he says.

"A museum needs a minimum of 3,000 to 4,000 quality works to be credible ... (and) is not meant to get rid of its acquisitions," he adds.

And even though top valued lots represented only a small proportion of the total market, they were key to the US and Britain maintaining top positions.

Eighty-three of the 125 sales worth $10 million or more were conducted in the US. These sales represent only 1 percent of lots but 75 percent of US sales volume.

One of the most spectacular auction results of the year saw Black Fire 1, a 1961 work by American abstract expressionist Barnett Newman, sell for $84 million in New York in May. It had a presale estimate of $39 million.

Artprice also says that the upper threshold for works could soon scale new heights. The $100 million ceiling for a single work was first breached in the 2000s. This month, a work by Gauguin sold privately for $300 million, according to the New York Times.

The $1-billion-mark could soon be reached, according to Artprice.

"Twenty years ago, America and Europe accounted for more than 95 percent" of sales, says Ehrmann, whereas today, buyers are active "on all continents without exception".

Art, he says, "has become an investment category in its own right, reliable, stable over time and much less prone to turbulence that the stock market".