Delisting is the removal of a listed security from a stock exchange.
Reasons for delistings:
- Companies are bought by a private equity fund;
- Companies cannot put up with the regulatory burden of being a public company;
- Companies bankrupt;
- The industry disappears (i.e. consumer cameras, Kodak);
- M & A happens;
- The company is relisted to another exchange;
- Other reasons.
Trivia:
https://www.statista.com/statistics/294296/nasdaq-delistings-reasons/