Clayton County

Clayton reduced residential property values by about $2 billion in 2010. The 22 percent reduction was the biggest drop in values among the five counties evaluated.

Despite the steep reductions, the county’s typical assessment was more than 7 percent above market value, as determined by sales.

Comparison of county appraisals to sale prices showed Clayton over-valued the typical property in one ZIP code, 30281 in Stockbridge, by nearly 14 percent but undervalued the typical property in ZIP code 30215 in Fayette County by 2.4 percent.

Cobb County

Cobb County reduced residential values by $5.1 billion, or more than 10 percent, in 2010.

The typical Cobb appraisal was nearly 7 percent below market value, as determined by sale prices.

The county overvalued the typical property in ZIP code 30157 near Paulding County by nearly 5 percent. The typical county appraisal in ZIP code 30067 in Marietta was nearly 10 percent under market value.

DeKalb County

DeKalb County reduced residential property values by $689 million in 2010. The 1.7 percent reduction was the smallest among the five counties studied.

DeKalb’s typical appraisal was more than 25 percent above market value, as determined by sale prices, primarily because the county did not fully account for distressed sales.

In one ZIP code, 30032 in Decatur, the typical county appraisal was 138 percent above market value. In 30307, east of downtown, the typical appraisal was 18 percent below market value.

Fulton County

Fulton County lowered residential values by $5.1 billion, or 6.7 percent, this year.

The county’s typical appraisal was about 2.6 percent below market value, as determined by sales prices.

Fulton overvalued the typical property in ZIP code 30326 in Buckhead by 14.5 percent. The county undervalued the typical property in ZIP code 30314 in Bankhead by more than 28 percent.

Gwinnett County

Gwinnett County cut residential property values by $4.8 billion, or 9.8 percent, in 2010.

The county’s typical appraisal was 2.5 percent above market value, as determined by sale prices.

In ZIP code 30093 in Norcross, the typical Gwinnett appraisal was nearly 21 percent above market value. The typical appraisal in ZIP code 30360 near Doraville was nearly 9 percent below market value.