Know-How Exchange : Advertising/PR

Does Anyone know of any data regarding the response rate to advertising when using a unique URL landing page for tracking? We are measuring a national print campaign, and are using landing pages to track the response by publication. For example, a URL would read oursite.com/thismagazine, or oursite.com/thatmagazine for each seperate publication.

Is there significant breakage on the response measurement because people just type in the oursite.com, or does using the unique URL discourage response in any way?