Ackman's Pershing Square Capital Management dumped roughly 10% of its stake in its largest and longest-held position.If there's one thing Wall Street doesn't lack, it's data. Between earnings season and monthly economic data releases, it can be easy for investors to get overwhelmed and miss something important.Roughly five weeks ago, during the heart of earnings season, what's arguably the most important data release of the quarter occurred. I'm talking about the May 15 deadline for institutions to file For ...