Root Soars 192% in Best Day Ever as Firm Turns Its First Profit

Root Inc. shares are having their best day ever on Thursday after the auto insurance platform announced that it had turned profitable for the first time in its history.

The Columbus, Ohio-based firm’s stock price soared as much as 192%, its biggest intraday advance on record. It has since trimmed some of those gains but was still up more than 150% at mid-session, jumping to around $103 from Wednesday’s close of $40.49 and adding almost $1 billion in market capitalization. The shares have soared roughly 875% this year.

In addition to reporting third-quarter net income of $23 million, reversing ...