ComScore Offers Potential and Actual Reach

ComScore said today it changed the way it's reporting on ad networks, effective with the August 2008 data. You'll get a chance to see the changes when they are released in mid-September.

Where previously comScore only provided data on unique audience, the new reporting will provide two sets of data measures: "potential reach" and "actual reach."

Potential reach is defined as "a calculation of unduplicated visitors all sites with which each ad network has contracted to deliver advertising," according to a comScore statement.The information will be based on written documentation provided by each of the networks.

Actual reach will represent the number of ads served by the network during a stated reporting period. Networks must provide comScore with identification protocols defined by the research firm for rendered ads to participate in the actual reach report.

See for yourself. Here's a look at comScore ad network rankings from earlier this year.