Press Release

comScore Responds to IAB Open Letter

RESTON, VA, April 23, 2007 – comScore, a leader in measuring the digital world, today announced the following response to the recent IAB Open Letter:

comScore welcomes the objective outlined in the IAB Open Letter of achieving transparency in panel methods for measuring the size of online audiences. comScore has already had positive and productive discussions with the IAB to initiate a thoughtful and cooperative process for achieving greater transparency and understanding the root cause of the difference between Web site server logs and panel-based measurements.

As part of our efforts to achieve transparency, we have opened our methodology and processes to an evaluation by the Advertising Research Foundation. We are in the final stages of this evaluation 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.

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.

Dr. Magid Abraham, President and CEO of comScore commented: “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 measurement standards for all participants.”


About comScore

comScore, Inc. is a global leader in measuring the digital world. This capability is based on a massive, global cross-section of more than 2 million consumers who have given comScore permission to confidentially capture their browsing and transaction behavior, including online and offline purchasing. comScore panelists also participate in survey research that captures and integrates their attitudes and intentions. Through its proprietary technology, comScore measures what matters across a broad spectrum of behavior and attitudes. comScore consultants apply this deep knowledge of customers and competitors to help clients design powerful marketing strategies and tactics that deliver superior ROI. comScore services are used by global leaders such as AOL, Microsoft, Yahoo!, Verizon, Best Buy, The Newspaper Association of America, Tribune Interactive, ESPN, Fox Sports, Nestlé, MBNA, Starcom USA, Universal McCann, the United States Postal Service, Merck and Expedia. For more information, please visit

Andrew Lipsman
comScore, Inc.
+1 312 775 6510


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