The research will be based on an integrated panel of one million US internet users who have agreed to let ComScore continuously measure their online behaviour and match that to the in-store transactional data held by Dunnhumby, which is collected via store loyalty cards.

ComScore chairman Gian Fulgoni said consumer goods marketers currently invest millions in brand websites with “no visibility into whether these assets are attracting the brand and category buying segments they are targeting”.

“The aim of this important study,” he said, “is to quantify the real value of visitors to various brand websites, identify the most valuable content that can be provided on the site, and provide actionable insight into where else on the internet marketers can best reach their brand buyers and prospects.”

Results are due to be published in the spring. The research has the endorsement of the Grocery Manufacturers Association and the Food Marketing Institute.