At the start of the 1910s, the decade would begin with the Panic of 1910–1911 stifling economic growth for a lengthy period of time. History would later take its course on July 30, 1914; as the average stood at a level of 71.42 when a decision was made to close down the New York Stock Exchange, and suspend trading for a span of four and a half months. Some historians believe the exchange closed because of a concern that markets would plunge as a result of panic over the onset of World War I. An alternative explanation is that the Secretary of the Treasury, William Gibbs McAdoo, closed the exchange to conserve the U.S. gold stock in order to launch the Federal Reserve System later that year, with enough gold to keep the United States on par with the gold standard. When the markets reopened on December 12, 1914, the index closed at 74.56, a gain of 4.4 percent. This is frequently reported as a large drop, due to using a later redefinition. Reports from the time say that the day was positive. Following World War I, the United States would experience another economic downturn, the post-World War I recession. The Dows performance would remain unchanged from the closing value of the previous decade, adding only 8.26%, from 99.05 points at the beginning of 1910, to a level of 107.23 points at the end of 1919.

How many days after the New York Stock Exchange suspended trading, did it reopen?
135