Vacancy for rental housing units in the Denver metro area stood at 5.5% in the 4th quarter of 2009, according to a report conducted by the Colorado Division of Housing. Of the counties in the measure, Boulder/Broomfield boasted the highest average rent ($1,631.30) and Douglas the lowest vacancy rate (3.0%), while Denver posted the lowest rental rate ($952.27) and the highest vacancy (6.8%). The average monthly rental rate for the period increased from the year-ago measure of $995.24 to post $1,016.77.