What defines a secondary trading area?

The correct choice highlights that a secondary trading area is defined as encompassing 20 to 30 percent of a store's sales. This concept is essential in retail location planning, as it reflects the market reach of a store beyond its primary trading area, where a significant portion of its customers might reside.

In a retail context, primary trading areas usually capture the bulk of the customer base, while secondary trading areas extend the reach to those customers who may travel a little farther to shop. The percentage given (20 to 30 percent) indicates the portion of total sales attributable to customers who are not the store’s main demographic but still contribute meaningfully to overall sales volume, thus illustrating the importance of understanding customer distribution in relation to retail strategy.

Other options do not capture this specific economic concept of sales contribution in terms of geographic customer presence and behaviors. For instance, the percentages associated with other options do not correctly identify the characteristics of a secondary trading area in the context of customer sales behavior.