The Department of Justice notes that the HHI between 1,500 and 2,500 points to be moderately concentrated, and consider markets in which the HHI is in excess of 2,500 points to be highly concentrated.
http://www.justice.gov/atr/public/guidelines/hhi.html
http://www.justice.gov/atr/public/guidelines/hmg-2010.html#5c
CFAI, you’re frakking up.