Not all segmentation schemes are useful. We could divide buyers of table salt into blond and brunette customers, but hair color is irrelevant to the purchase of salt.
Furthermore, if all salt buyers buy the same amount of salt each month, believe all salt is the same, and would pay only one price for salt, this market is minimally segmentable from a marketing point of view.
Rating Segments To be useful, market segments must rate favorably on five key criteria:
Measurable. The size, purchasing power, and characteristics of the segments can be measured.
Substantial. The segments are large and profitable enough to serve. A segment should be the largest possible homogeneous group worth going after with a tailored marketing program.
Accessible. The segments can be effectively reached and served.
Differentiable. The segments are conceptually distinguishable and respond differently to different marketing-mix elements and programs. If married and single women respond similarly to a sale on perfume, they do not constitute separate segments.
Actionable. Effective programs can be formulated for attracting and serving the segments.