Measures of program trends indicate how frequently or consistently audiences watch:

• A series of program episodes, or
• Portions of a given program episode.

These measures indicate the level of loyalty that audiences have for programs. It is believed that programs with highly loyal audiences are better suited for the placement of advertising for two reasons:

1. Audiences will be more involved in the program content, and thus retain more of the advertised message.
2. Audiences will associate the appeal of the program with the advertised product.

Several measures of program trends are supported by the Audience Watch.

• Retention The portion of an audience that saw an episode of a program, and also saw subsequent episodes of the same program.
• Loyalty The portion of an audience that saw an episode of a program, and also chose to watch subsequent episodes of the same program when given an opportunity to do so.
• Defection The portion of an audience that saw an episode of a program, and then chose not to see subsequent episodes of the same program when given an opportunity to do so, but watched competing programs at the same time the program is being aired.
• Experience The portion of an audience that was exposed to prior episodes or prior quarter hours of a program.
• Quad Analysis The division of a program audience into four distinct groups based on two factors: 1) Their frequency of episode exposure (week-to-week retention), and 2) The average length of episode exposure (in-program retention).

The distinction between retention and loyalty is a subtle but an important one. Retention measures frequency of episode viewing regardless of other activities. Loyalty measures only viewing if given an opportunity to see. Mowing the lawn while a program is airing is not an indicator of disloyalty to the program, and does not affect the loyalty measure. It does affect the measure of retention, however.

Loyalty and defection are just different ways of looking at the same measure. People who are watching television have been either loyal or disloyal. There is no third group. Thus:

A theoretical description and analysis of television program loyalty can be found in A Network Television Viewing Choice Model.