Those businesses made up 96 percent of Zillow's total revenue in 2018, and 88 percent in the fourth quarter, with the Homes segment just getting off the ground and mortgages not yet in their own category. Barton, CEO for the company's first five years, will oversee Zillow's radical transformation. Barton is returning to the job because of his affinity for "big swings", and he will take over for Spencer Rascoff, who is stepping down from the CEO seat but will remain on the board.