1. Demand
The number of units of a product sold in a market over a period of time. For example, six thousand library books were circulated in Branch X's market area last year.
2. Demarketing
The process of reducing the demand for a product--or decreasing consumption
3. Ordinal Scale
A measurement in which numbers are assigned to attributes of objects of classes of objects to reflect the order.
4. Output Evaluation
An objective measure of use performance, such as circulation per capita of a library population, reference transactions per capita, etc.