NIO stock has sunk back under the $20 mark, with its shares falling almost 4% at the end of last week. Is now the time to buy? Over the past six months, NIO(NYSE: NIO)stock has halved in value. This disappointing trajectory has reversed the astronomical growth that NIO experienced in 2020, when its shares rose from under $5 to over $60. Being a long-term holder of NIO stock, these share price movements have been pretty tough to watch. 2022 alone hasn’t been much better, with the shares down 41% year-to-date. So, at under $20, are NIO shares a bargain? Or should I stay away from buying more for my portfolio? The bull case The primary reasons why I like the look of NIO stock at its current price are the stellar results the company has been able to keep issuing. Between 2020 and 2021, ca