Within the methodology of the system, each site to be evaluated is given a rating number of between 0 and 100. This is according to the degree of overall visitor satisfaction reported with the site. The satisfaction score itself is attained by quantifying a range of consumer inputs, including whether people found what they were searching for and whether they would revisit.

Speaking about the new rating system, Pete Comley, Managing Director of Virtual Surveys, said "Increasingly sites need to assess how they perform versus competitors. Our model allows for the first time an independent measure to be obtained of site effectiveness. The VSI is a major step forward. It has sometimes been difficult to interpret Web visitor surveys because of the biases caused by response rates of 20%-30%. VSI takes this factor out of the equation and, with one simple number, allows you to see how your site is performing."

Comley has also likened the company’s development to that of similar indices in advertising research. "Pre-testing research was revolutionised two decades ago by companies using indices of ad effectiveness, and we expect to see the same usage here in website research."