This is for apartments in buildings of 50 or more units — big apartment buildings (as opposed to single-fam homes, townhomes and condos that were rented out one-by-one). But it tells you plenty about how rents did in 2015.
The data is from Tom Cain's "Apartment Insights Washington" firm.
The report noted that in the most-expensive rental submarkets, such as in downtown Seattle and downtown Bellevue high-rises, rents SOFTENED for first time in the 4th quarter. That may give the first hint that all of those new-construction apartment projects are finally starting to meet demand in some submarkets.