The green shaded area on the map shows the properties the state reassessed starting Jan. 1. Credit: FROM MARYLAND DEPARTMENT OF ASSESSMENTS AND TAXATION

New property assessments for about one-third of Montgomery County were mailed on Thursday, showing an aggregate increase in value of about 8 percent starting Jan. 1.

The values of those properties increased from $63.6 billion on Jan. 1, 2015—the last time the assessments were set—to $68.9 billion as of Jan. 1, 2018.

Maryland divides its assessments into three-year periods, revaluing one-third of each county and Baltimore City at a time.

The latest round of property assessments in Montgomery County are in eastern, northern and central parts of the county. The area includes Rockville, Olney, Gaithersburg and some northern sections.

Overall, newly assessed properties across Maryland rose about 7.7 percent from the last period, according to a press release from the state’s Department of Assessment and Taxation. That includes 5.8 percent for residential property and 12.7 percent for commercial property.

In Montgomery County, the breakdown is 3.9 percent for residential property and 17.4 percent for commercial property.

The largest jump, by far, was in Prince George’s, where the aggregate increase was 17.5 percent; about 86 percent of all parcels in the newly assessed area rose in value. Sixty-three percent of Montgomery County’s newly assessed properties gained value.

Aggregate values dropped in just two counties—Dorchester and Talbot.

A chart shows that Montgomery County assessments in certain areas went up 65.0 percent in 2005 and 63.3 percent in 2006. The increases went down to 43.4 percent in 2007 and 16.2 percent in 2008.

For the next four years, aggregate property values dropped, before slowly rising again start in 2013.

The last time the same section of the county was reassessed, in 2015, the aggregate increase in value was 18.7 percent.

Maryland law caps the annual increase in taxable assessment at 10 percent for property owners who meet certain qualifications. If an assessment goes up, for example, 9 percent, it will be phased in evenly over a three-year period.

Counties may pass lower caps, and almost all do. Montgomery, Calvert and Somerset are the only three counties in Maryland to stick with a 10 percent cap, a Department of Assessments chart shows.