D.C. Mun. Regs. tit. 9, r. 9-304
The Mayor shall annually prepare an assessment-sales ratio study for major classes of property for the entire District and for major classes of property within each assessment area for which sufficient data is available, as determined by the Mayor. Results of the study shall be published in the D.C. Register and made available to the news media.
The Mayor may designate geographic assessment areas for purposes of analyzing market values. An "assessment area" is a geographic area within the District which has been designated by the Mayor as an area for assessment purposes.
The boundaries of the assessment areas may be changed as necessary in order to reflect changing economic or other conditions which have a bearing on the market value of properties.
For the purpose of analyzing market values, the Mayor may, if he or she deems it desirable, analyze values by types of property (for example, all motels or all hotels) rather than only those types of properties located in a geographical area.
Descriptions of the boundaries of assessment areas or maps showing these boundaries shall be made available to the public during normal business hours.
D.C. Mun. Regs. tit. 9, r. 9-304