The firm has submitted a proposal for a new “person-centric measure for website server measurement” to be considered by the Audit Bureau of Circulation Electronic’s Internet Technical Group in a bid to have it agreed as an accepted metric for the audited measurement of unique visitors.

ComScore’s proposal involves calculating cookie deletion rates from an online panel of web users and applying the necessary adjustments to website server data in an attempt to provide a more accurate picture for the number of visitors a site gets in a given time frame.

Server data alone often overstates the number of unique users or browsers logging on to a site as it relies on cookie counts, and frequent cookie deletion by users can lead to more than one cookie being assigned to the same device.

ComScore said that on its UK panel “an average of 2.4 cookies per site appeared across all PCs during the course of a month, indicating that relying on website server data alone is likely to be exaggerating the size of a site’s audience by a factor as high as 2.4x, or an overstatement of 140 per cent”.

Effectively, ComScore is seeking industry acknowledgement of its new Media Metrix 360 approach to audience measurement – a fusion of panel and server-side data that was launched this summer in the US and is now being introduced in the UK.

The proposed metric will be considered at the next ITG meeting before being put to Jicwebs, the joint industry committee responsible for agreeing site-focused, census-based web measurement standards, later this month.

In a statement, ABCe said: “Web analytics, including the use of cookies, continually evolve and we look forward to ensuring that ComScore’s contribution in that debate is explored at the ITG and Jicwebs.”

Current Jicwebs standards permit sites to report unique user/browser numbers based on counts of either IP+User-Agent information, cookies or registration IDs. At that next Jicwebs meeting ABCe said the committee will clarify that daily unique user/browser data “eliminates the relevance of cookie deletion, to all intents and purposes” and that the unique user/browser metric “is expressly aimed at counting devices (not people)”.

ComScore was one of four companies who bid to become the UK Online Measurement Company’s (UKOM) supplier of web audience measurement data. Nielsen was appointed last month and the first data is expected in January. UKOM is pitching for the data to become the official planning currency for online media.