Fast fashion — the idea that clothing trends change rapidly and so should the stock of retailers — was pioneered by brands like Zara, H&M and Forever 21, and predicated on speedy supply chains and low cost production. Now, a little-known Chinese brand named Shein is disrupting the fashion industry by using slick social media campaigns and aggressive promotions on TikTok, Facebook and Instagram to sell ultra low-cost clothing to teens and college-aged consumers throughout the world. An