The RTB 500 index is compiled by OwnerIQ based on real-time data. It was modeled on Wall Street’s S&P 500 index, and the math is similar, except that instead of using a weighted “float” of publicly traded company stocks, the RTB 500 utilizes a weighted float of the number of impressions available from publishers in the index in the open RTB marketplace during the period of time calculated.

The 500 publishers were chosen because they are representative of the major advertising categories within the digital media marketplace.

The RTB 500 also publishes sub-category indexes with specific types of publishers that participate in the RTB marketplace and whose primary business models represent conventional media categories such as newspapers, magazines and network TV. The sub-category indexes do not reflect trading of their analog media impressions, just the portion of their digital inventory that is available in the open RTB marketplace. It is up to readers to determine how representative that is of their overall supply and demand. A minimum of 10 publishers are included in each sub-category.

The sub-categories were categorized by Owner IQ, but are consistent with standard site categories or genres found in syndicated research and planning tools commonly used by media buyers. The 500 publishers included are representative of the top domains by number of available opportunities seen within the exchange environments.