- April 25, 2007

Comscore Responds to IAB Open Letter

Magid M. Abraham, Ph.D.
Magid M. Abraham, Ph.D.

Recently, Comscore was asked by the IAB to provide clearer transparency with regards to our panel methods for measuring the size of online audiences. Comscore welcomes the objective outlined in the IAB Open Letter. We have already had positive and productive discussions with the IAB to initiate a thoughtful and cooperative process for achieving greater transparency and understanding of the root cause of the difference between Web site server logs and panel-based measurements.

We began working with the MRC several months ago as part of an audit of our methodologies to provide that transparency. We intend to continue that effort. We are also in the final stages of an evaluation of our methodology by the Advertising Research Foundation and hope that the results will be publicly released in the near future.

Comscore’s panel methodologies reflect the investment of millions of dollars and years of research and development. We are confident that they will stand the scrutiny of a third-party evaluation or audit.

As part of our own efforts at providing the Internet industry with insight into the various ways of counting online audiences, we recently published the results of a seminal study of the impact of cookie deletion on the accuracy of audience counts as obtained from Web site server logs.

The study revealed that cookie deletion is a serious threat to the accuracy of Web site server logs, leading to overstatements in the estimates of unique visitors as obtained from server logs by a factor of as much as 2.5. A representative group of industry experts agreed with our conclusions.

If you would like to view the complete findings of this study, please visit: http://www.comscore.com/press/release.asp?press=1389 .

Many of our clients are using Comscore’s panel data to adjust their own server log data so as to eliminate the overstatement caused by cookie deletion and we would hope that this approach becomes a standard practice within the industry.

We look forward to demonstrating the quality of the Comscore panel methodology to the IAB.

I want to assure the IAB members that Comscore is committed to the digital media industry and strives to provide, to the best of its abilities, accurate and unbiased measurement. We look forward to working with the IAB and the rest of the industry on establishing acceptable measurement standards for all participants.

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