In 1987, the DJIA plummeted more than 22% in one day, yet the next day, the volume of shares traded (600 million) created a new volume high record. By 1997, daily trading volume of shares exchanging hands reached one billion. In 2001, in the wake of the World Trade Center attack, the NYSE was closed for four sessions, the longest period of time the exchange was closed since 1933. Yet when the exchange reopened on September 17, 2001, the NYSE hit another record, with over 2.37 billion shares traded. In November 2013, the Intercontinental Exchange Group (ICE) acquired NYSE Euronext, creating the leading global network of regulated exchanges and clearing houses for financial and commodity markets.