As journalists dug through the Panama Papers, they uncovered a major secret for how the super-rich hide their money ... art. More than half of all art sales are private. Many of them are secret. We hear how tax-free warehouses around the world are used to hide billions.| Want to support 1A? Subscribe to our podcast and give to your local public radio station at donate.npr.org/1A. Email the show at 1a@wamu.org.