When it comes to international trade and finance, everyone pretty much speaks one language: the U.S. dollar. So when the Federal Reserve hikes interest rates and the dollar suddenly gets strong, it can cause huge headaches all over the world. Subscribe to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney Learn more about sponsor message choices: podcastchoices.com/adchoices NPR Privacy Policy

On today's show, we're answering listener questions from the Planet Money inbox. Like, who really benefits from retail coupons? And why are goldfish so cheap? Subscribe to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney Learn more about sponsor message choices: podcastchoices.com/adchoices NPR Privacy Policy