As of July 29, short interest fell to about 12.65 billion shares, from 13.058 billion shares as of July 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.

Shorting can also be part of a hedging strategy.

(Reporting By Sinead Carew; editing by Jonathan Oatis)