WASHINGTON— After declining for four years, a number of key trends — including the average size of the home and the number of bedrooms and bathrooms — reversed course in 2020 as a result of shifting buyer preferences in response to COVID-19. The average size home remained flat at 2,486 square feet, while the percentage of homes with four or more bedrooms and three or more bathrooms rose to 46% and 33%, respectively, rising closer to 2015 peaks, according to information from the National Association of Home Builders presented during the recent International Builders' Show, held virtually.