Hedge fund titan Bill Ackman today raised $4 billion in an IPO on the New York Stock Exchange — but it wasn’t for a company, or even for the firm that controls his hedge funds. It was for something called a SPAC, a special purpose acquisition company, and it was the largest SPAC IPO of all time. Dan is joined by Ackman to discuss why SPACs have become so popular and what Ackman has learned since 2012, when he used a SPAC to bring Burger King public.