Retailers would be wise to use first-party rather than third-party cookies if they want a more complete view of online visitor behavior, Coremetrics suggests, issuing findings from its LIVEmark Index, a benchmark performance-tracking service. ClickZ reports that the research found anonymous traffic accounts for 13.8 percent of traffic on retail websites using third-party cookies, whereas those that have adapted first-party cookies have an average of 0.6 percent anonymous traffic.

In May, Coremetrics competitor WebTrends released similar findings on third-party cookie deletion and plans to publish updated research.

"We are identifying the top three verticals most affected, one of which is retail," Corey Gault, public relations manager at WebTrends, told ClickZ News, adding that upcoming research would include statistics on sites using first- and third-party cookies simultaneously.

Coremetrics offers a solution for clients to migrate from third- to first-party cookies yet retain older profiles of customers.