A Demographic indicates which demographic ("slice of the overall population") a particular household belongs to (if any). It is used by the simulator to mark households on a city map.

There are two kinds of Demographic objects: Vacant and Occupied:

• The singleton object Vacant is used for indicating that a residence is empty and does not belong to any demographic.
• Occupied objects indicate that a residence belongs to a specific demographic; each different demographic is assigned a different Color. For instance, a residence may be "occupied by the red demographic", or "occupied by the blue demographic".

What exactly constitutes a demographic is unimportant for the purposes of this class. Demographics could be based on people's socioeconomic status, political views, ethnicity, age, or something else.

All Demographic objects are immutable.

The trait Demographic itself does not define any methods; it merely serves as a supertype for Occupied and Vacant.