The Group of Seven +405.25%

Howdy!

ArtPrice.com just released their Art Market Trends 2006. In it the only mention of Canadian art is the following:

This is one of the rare Modern movements to post such a sharp price inflation. The artists of the group of seven distinguished themselves by their love of landscapes and colour Even if they worked together from 1912, it was not until 1920 that the painters formed the artistic movement that renewed Canadian painting for twelve years. Their market remains focused on Canadian galleries and auction houses. For example, 100% of Lawren Stewart Harris’s lots sold at auction were sold in Canada. Since 1999 the artist’s index has progressed 624%. Illustrative of this rapid inflation, Mount Lefroy, an oil on panel from 1929, offered at CAD 200,000 – 250,000 on 25 May 2006 at Heffel (Vancouver) finally sold for CAD 1.45 million ($ 1.29 million). Same speculative effect on Frederick Horsman Varley, whose price index shot up 256% during 2006: Lynn Valley, the Pipeline Road, estimated at CAD 35,000 – 45,000, sold for CAD 120,000 at the same sale.

What I want to know, is how large is their database that enables them to quantify things to two decimal places? Or are they just assuming that the more decimal places they write, the more impressive everyone will think their calculations are?