New way to rank Web Sites from Nielsen

Looks like they are changing things a bit. 

Although Nielsen already measures average time spent and average number of sessions per visitor for each site, it will start reporting total time spent and sessions for all visitors to give advertisers, investors and analysts a broader picture of what sites are most popular.

 This will have an impact on advertising rates and increase the likelihood of a website trying to encourage interaction with its visitors and thus keeping on the site longer.