Of all the housing units in the US, renter-occupied residences accounted for 27.7%. While vacant housing units comprised 14.5% of the country's total housing inventory, units on the market for rent accounted for just 3.5% of the whole. By comparison, the national homeownership vacancy, at 2.6% in Q3, ticked down by 20 basis points over the past year, but remained relatively flat quarter-over-quarter.

Despite the tendency to concentrate apartments around metropolitan centers, the vacancy rate for rental units in major US cities was the same as the vacancy rate across national suburban markets, both at 11.2% in the third quarter. The rate outside of metropolitan statistical areas came in at 10.6%. Regionally, rental properties in the South tended to have the highest vacancies, 14.2% on average, whereas those in the Northeast were the lowest, at 7.5%.

On the revenue side, rents for residential units took a dip along with occupancies. According to the Bureau of Labor Statistics' Consumer Price Index, rental rates declined for the third consecutive month in September, this latest time by 60 basis points, on a seasonally adjusted annual basis.