From the April, 2019 issue of “Units” magazine, the top 10 cities where studio rent increased and decreased the most, Portland is #10. I suspect the article has a confusing column, the “$ Decrease” probably is the “Studio $ Average”. If that is the case, the arrival of Portland on this list is most likely due to the concessions made by new construction, close-in (expensive) studios. Most pre-2000 built properties with studios have rents lower than this average. Overall, I would call this a “new construction market correction” vs. a trend of decreased rents.
Or, the trend could be called: “New Construction Studio Rents Not As High As Developers Hoped”