I encourage you to start by reading this article from the SEC: http://www.sec.gov/investor/pubs/leveragedetfs-alert.htm And here's a great chart illustrating this point again: http://stockcharts.com/c-sc/sc?s=VXX&compare=XIV&id=t06942317430&r=1366725661668 As you can see, VXX dropped 16% during this time period. You would assume that XIV would have gained 16%, but instead is essentially flat. The magic of decay!