The chart shows the annual average premium prices of lots sold within a certain collecting category, which are calculated by dividing the total sales volume of the premium prices of all lots sold by the amount of lots sold. artnet defined peer groups or artists representing certain collecting categories. To be included in artnet’s peer groups, artists need to have sold either at least 10 lots at USD 10,000 or more, or at least 40 lots at USD 5,000 or more, or at least 3 lots each year since 2006 of which at least 2 were sold over USD 5,000. Our Photography art peer group consists of 445 artists. For 2009, the data included in the calculations is current through the 15th of June. The charts will be updated every three months.

The data is culled from the artnet Price Database, which has collected auction sales results for over twenty years.

Prices are stated in USD in order to facilitate comparison and analysis of the market reports. When sales took place in another currency, the conversion of that amount into USD was done on the basis of the average conversion rate applicable on the day of the sale.

Although most auction houses these days report transactions in prices that include a buyer’s premium, some auction houses report only the hammer price. Based on an analysis of historical auction catalogs, we apply a formula to all records with hammer prices to estimate the effect of a buyer’s premium. All prices used in the charts are either reported in or equated to hammer price plus buyer’s premium.