What happens to applicationStorageDirectory on App update? (iOS App Store)

I have an iPad app being sold in the iOS App Store. I use applicationStorageDirectory to save some XML files locally to the iPad (stuff like user’s high scores when playing in offline mode).

What will happen to these files for my users if I upload a new app update to App Store? Will they get deleted because the update is a fresh install of the app, or will they be left alone?