Do you know what page your site visitors leave on?
It might be a good idea to track which page(s) your site visitor leaves on. Also, if there is a way to tell if a page opens over top of your own site, that would be good to know. For instance, maybe instead of clicking on an ad to leave, they open a bookmarked page over top. Knowing which pages were being used for exit could allow you to tweak your site as that specific page(s) might have caused the site visitor to disconnect from the site emotionally.