Marc Benioff, founder and co-CEO of Salesforce, loves tackling big challenges. In starting the company, he set out to prove that selling software as a subscription service rather than as a one-off purchase could become the predominant way that large companies buy it. He succeeded: Salesforce now has a market capitalization of $143 billion. 

I’m predicting that in 2020 Benioff will step aside as co-CEO to become executive chairman, so he can be freed to take on a new set of challenges. In particular, he has demonstrated his interest in fixing a variety of social problems ranging from economic inequality and the gender pay gap to homelessness and health care.