Which of the following measures is a reliable indicator of the effectiveness of a promotional program?

The change in customer behaviors serves as a reliable indicator of the effectiveness of a promotional program because it directly reflects how consumers are responding to the marketing efforts put in place. When a promotional program is successful, it typically leads to an increase in customer engagement, purchases, or changes in brand perception. This shift in behavior—whether it be more repeat purchases, increased inquiries, or higher foot traffic—indicates that the promotional activities have resonated with the target audience.

In contrast, vendor adjustments of invoice terms relate more to the internal financial processes rather than consumer behavior; a business slump at a local pro shop reflects broader economic or market conditions that may not necessarily indicate the success of a specific promotional effort; and while Facebook survey results can provide insights, they may not effectively capture the comprehensive changes in consumer behavior that indicate actual performance and acceptance of the promotional campaign. Thus, monitoring changes in customer behaviors provides direct evidence of how successful the promotional strategies have been.