Influence Index is defined as the relative level of influence that exposure to one or more advertisements in an advertising schedule has on purchasing decisions.
- The minimum value is zero, meaning that previous exposures to advertisements in an advertising schedule have no influence on current purchases.
- The maximum influence index value is 100%. If a person is at the 100% level of influence, the influence on purchasing decisions which results from being exposed to advertisements will not increase with additional advertising exposure.
In the figure below, for example, we show the theoretical influence that an advertising campaign would have on a person if:
- The person was exposed every day for 28 days
- The person absorbed 15% of the remaining unlearned message content with each exposure
- The person does not forget message content over time (obviously unrealistic)
Figure 1 - Recency/Recall Influence Plot
As you can see, under these assumptions, after about 21 days, the incremental influence that additional ads have on the person is minimal. By that point the person is at a 100% level of influence. This does not necessarily mean that the person is committed to using the advertised product. It only means that additional ads will not further influence the decision to use the product.
See Influence Index.