From two weeks ago, XIV price have begun to deviate from its NAV. Now it's 3% higher than its NAV or SVXY who traces the same index. That happened to TVIX several years ago as well. At that time, TVIX's price was even more than 10% higher than its NAV. This is quite uncommon for a popular ETF with a big volume; you can't manipulate the price of such ETF. I don't know if anybody has any explanation of that. The only thing I can figure out is that XIV and TVIX are both issued by VelocityShares.