Planet Money had an episode about this just last month. https://www.npr.org/sections/money/2018/01/10/576879734/episode-489-the-invisible-plumbing-of-our-econo

Planet Money had an episode about this just last month. https://www.npr.org/sections/money/2018/01/10/576879734/episode-489-the-invisible-plumbing-of-our-economy https://www.npr.org/sections/money/2018/01/10/576879734/epis...