Here's how long it has been since the Yankees were in the postseason: Their last playoff game took place at Yankee Stadium on October 8, 2007. The very next day, a few miles south, the Dow had its highest closing ever: 14,164.53.
With the Yankees an also-ran, the Dow plummeted to 6,547 on March 9 of this year, the same day that A-Rod went under the knife.
Then A-Rod got healthy and the Yankees started rolling. With the Bombers back in the playoffs, the Dow closed today at 9,748.55.
The first time the Yankees won two titles in a row - 1927 and 1928 - the streak ended in 1929. That October, the stock market crashed.
1987 was not a notable year for the Yankees as far as I know, so I will blame that year's crash on the failure of the 1986 Mets to repeat.