Here's Why Duolingo Stock Popped Today

The language-learning app is moving into a prominent index.Shares of language-learning app Duolingo (DUOL 6.97%) popped on Thursday after the stock was added to the S&P MidCap 400 index. As of 10 a.m. ET, Duolingo stock was up 6% but it had been up as much as 12% in earlier trading.Should investors actually care about this?Investors should concern themselves with news regarding Duolingo's business. By contrast, this news has more to do with the stock. Duolingo stock will officially be a member of the S&P Mi ...