Short interest on the New York Stock Exchange rose 1.8 percent in late May, the exchange said on Tuesday.

As of May 29, short interest rose to about 21.931 billion shares, compared with 21.553 billion shares as of May 15.

Investors who sell securities short borrow shares and then sell them, expecting the stock to fall so they can buy the shares back at the lower price, return them to the lender and pocket the difference.