For over 200 years the U.S. Immigration policies have determined who the U.S. lets in, and who is shut out. NPR’s Tom Gjelten explains. • Read or listen to "What Does Chain Migration Mean? We Get An Explanation" at https://n.pr/2rnvDun ------------------------------------------------------ Subscribe to NPR on YouTube: null Follow NPR elsewhere, too: • Twitter: https://twitter.com/npr • Facebook: https://www.facebook.com/NPR • Instagram: https://www.instagram.com/npr/ • Tumblr: http://npr.tumblr.com/ • Snapchat: https://www.snapchat.com/add/npr ABOUT NPR NPR connects to audiences on the air, on demand, online, and in person. More than 26 million radio listeners tune in to NPR stations each week and more than 36 million unique visitors access NPR.org each month making NPR one of the most trusted sources of news and insights on life and the arts. NPR is also the leading publisher of podcasts, with 36 original shows and an average of 4 million listeners per week. NPR shares compelling stories, audio and photos with millions of social media users on Facebook, Twitter, Instagram, Pinterest, YouTube and Snapchat; NPR News and NPR One apps, online streaming, podcasts, iTunes radio and connected car dashboards help meet audiences where they are. NPR's live events bring to the stage two-way conversations between NPR hosts and the audience in collaboration with the public radio Member Station community. This robust access to public service journalism makes NPR an indispensable resource in the media landscape.