Application_End() and Server.MapPath()

I wrote the following code in Application_End. It appeared as if Application_End was not firing

XmlDocument statDoc = new XmlDocument();
string path = Server.MapPath("~/App_data/Stat.xml");
statDoc.Load(path);
statDoc.SelectSingleNode("/Stats/Stat[@id=\"Visits\"]").Attributes["Count"].Value = Application["Visits"].ToString();
statDoc.SelectSingleNode("/Stats/Stat[@id=\"Hits\"]").Attributes["Count"].Value = Application["Hits"].ToString();
statDoc.Save(path);

With the help of this forum post, I was able to solve the mystery. Server.MapPath() does not work within Application_End() or Session.End()