This Is the World's Hottest Car Company Andrei Stanescu / iStock Editorial via Getty Images Very few Americans have heard of Nio Inc. (NYSE: NIO), which can count itself as one of the world’s most successful car companies. Its stock has been up 26% in the past month, while the S&P 500 has been flat.Nio is one of China’s dozen up-and-coming car companies. Smaller than rival BYD, it still has the advantage of operating in the world’s largest electric vehicle (EV) market.In April, Nio delivered 15,650 vehicl ...