Billionaire Ken Griffin, who bought the most expensive US home for $238 million (₹1,700 crore) in New York, is the CEO of $28-billion Citadel hedge fund. The 50-year-old, who has a $9.6-billion fortune, began trading from his Harvard University dorm room in 1987 and founded Citadel in 1990. Griffin owns art collection and real estate worth around $700 million each.