Share is an audience measurement term that identifies the percentage of television households with sets in use which are viewing a particular program during a given time period. If the total TV audience is represented by a pie, the audience for each program is a slice or share of that pie. The slices are not equal, however, since audience share varies widely according to the relative popularity of each program. Share is a comparative tool; it allows station and network executives to determine how well their programs are doing when compared with competing programs on other broadcast or cable channels.

Share is closely associated with rating, another measurement term. Both terms are derived from the same estimates of audience size, but the percentage quotient is calculated differently. Share measures the percentage of TV viewers who are actually watching a particular program, while the rating for a program calculates the percentage of all television households--both those using TV and those not using TV.

For example, station WXXX airs Jeopardy at 7 p.m. Sample data estimate that 10,000 or 10 percent of the city's 100,000 TV households are viewing that program. Some 40,000 households are viewing other programs, but another 50,000 are not using their TV sets. Since 10,000 of the 50,000 active viewers (20%) are watching Jeopardy!, that program has a share of 20 even though its rating (the percentage of TV households) is only 10.

Electronic media trade journals generally report both rating and share. Rating is expressed first and is given to the nearest tenth of a percent. Share follows and is rounded to the nearest whole percent. For example, an audience estimate for 60 Minutes may report a 13.0/28; i.e., 13% of the total TV households (the rating) and 28% of the viewing audience (the share).

If every television household was using TV during a given time period, the share and the rating would be equal. But since this never happens, the share for any program is always greater than its rating because different divisors are used to calculate the two equations.

The gap between share and rating is greatest during periods of very light viewing. An early morning newscast with a share of 30 and a rating of only 3 is competing very well against other programs in the same time block even though the total number of viewers for all programs is small.

Share is useful as a comparative tool during virtually any portion of the day, however. When a program gains share, it usually does so at the expense of competing programs since the total audience for television during any given day-part is relatively stable.

Share can also be used to illustrate programming trends. One network may average its share of successive programs to illustrate its dominance on a particular weekday night. A new broadcast or cable network may average its share across an entire season to illustrate its increasingly competitive position over a previous season.

Share can be used to demonstrate industry trends. For example, the combined share of ABC, CBS, and NBC for the 1980-81 programming year was 90. This meant that 90% of the viewing audience was watching one of these three networks. The remaining 10% of the audience was distributed among independent stations, public television, and the few cable networks then operation. By 1993-94, combined network share had dropped to 60, primarily because the cable networks collectively had captured one-third of the network viewers. Some industry observers predict that network share will continue to decline; others believe the erosion of network share has been halted and possibly reversed. A study of network share measures the competition between traditional broadcasters and their new technology competitors.

Unless otherwise specified, share refers to the total universe of television households. Share can be used in demographics breakouts, however. A morning talk show may have a 2.2/20 for women 18 to 34 years of age. That would be the rating and share for this particular demographic grouping.

-Norman Felsenthal