Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, investor, researcher, humanitarian, and philanthropist. He co-founded Microsoft alongside Bill Gates in 1975, which helped spark the microcomputer revolution and later became the world's largest PC software company. In March 2018, Allen was estimated to be the 44th-wealthiest person in the world according to the Forbes annual list of the world's billionaires, with an estimated net worth of $21. 7 billion, revised at the time of his death to $20. 3 billion.