Have you ever gone to buy something online, and once you see the shipping price decide not to buy it anymore? Are you more likely to search for a product offered on a website with free shipping site wide, rather than a website not offering free shipping site wide?
I often shop online especially for clothing or school books. Most of the time i do get free shipping but there are many occasions when i get a product and see the shipping price and decides its jsut not worth it. I would definitely be more likely to buy something if i knew it came with free shipping. I would even settle for a deal like spend more then $25 and shipping is free. However a website that does charge for shipping would not stop me from visiting or purchasing from the website. I do believe that shipping costs do influence customer purchases overall and should be studies by marketers.