The 179,444-unit Northern Virginia apartment market registered a fourth quarter 2015 vacancy rate of 4.7%, up 20 basis points from the prior quarter and up the same amount over 12 months. January data give a rate of 4.8%. Average asking and effective rents increased by 0.2% in the fourth quarter of 2015, according to Reis. The average asking rent was $1,682 per month, and the effective rent $1,641 per month. These rates are both up 2.4% for the year. January data show 0.4% and 0.5% asking and effective rent gains.