Adverse selection is the problem that arises when the people or firms who are most eager to make a transaction are the least desirable to parties on the other side of the transaction. when this happens markets fail due to the problem of:

The market fail because of those least desirable parties because in order for the problem to be prevented, the people involved or the firm should have the determination of doing their job such as having to make the transaction, if they are not interested, then there will be a marketing failure.