Share is a relative measure of viewing. It is the percentage of homes watching a station among Homes Using Television during the time period. A share is obtained by dividing a program's rating by the HUT. In the above example (and rounding the numbers) seven divided by 61 is a 12 share. Share is relative because the denominator changes with each half-hour or quarter-hour HUT change. On Sunday mornings when HUTs are low, "Sesame Street" might have a two rating and a 60 share. Shares tell how a station is doing against the competition at a specific time.

Why do the share above add to 108 instead of 100 percent? Because 55 percent of Portland's homes contain two or more TV sets and sometimes they are tuned simultaneously to different channels. In such cases, each station is credited with viewing, but the HUT is still one home. Frequently, all sets in a household are tuned to the same channel. In this case, only one home is assigned to the viewing station, and the HUT remains one.

Ratings enable public TV stations to assess performance from sweep to sweep and year to year. They also permit comparison of programs' performance. Ranked ratings show a station how attractive its programs are to viewers in the market. But markets vary. here are the top 10 programs and their timeslots in two different markets in November.

Table 2 Top Ten Program Rankings
Station X/DMA A Day Time Rating Station Y/DMA B Day Time Rating
1. This Old House Sat 5:30 8.2   1. Discovr/Science Wed 7:00 7.0
2. Frugal Gourmet Sat 5:00 6.7 2. NOVA Tue 8:00 4.5
3. Holiday/Stewart Wed 8:00 6.6 3. Moyers, Sec Gove Wed 8:00 5.0
4. NOVA Tue 8:00 4.6 4. Wild America Thu 7:30 4.0
5. Victory Garden Sat 4:30 4.5 5. Sgt. Pepper Wed 9:00 4.3
6. Discvr/Science Wed 8:00 4.5 6. Lawrence Welk Sat 7:00 3.9
7. Julia Child & Co Sat 4:00 4.2 7. Buster Keaton Wed 8:00 4.0
8. First Eden Mon 8:00 4.5 8. Cousteau Spcls Tue 7:00 3.1
9. Washington Wk Fri 8:00 4.4 9. This Old House Sun 5:30 3.3
10. Wall St Wk Fri 8:30 4.3 10. In Perf/Wt Hs Wed 7:00 3.4

DMA A's top 10 list ranged from an 8.2 rating for the first-ranked program, "This Old House" to a 4.3 for the 10th-ranked program, "Wall Street Week." In Denver, "Discover/Science" gathered a 7.0 rating, "In Performance at the White House," a 3.4.

Note that in DMA A, four of the 10 top audience-attracting programs were how-to programs scheduled on Saturday afternoon. This is a typical of many markets lately, as public TV stations find niches of non-prime "premier time" that can attract larger audiences than their prime-time programming. DMA B, a market classified by the Television Ratings Analysis Consortium (TRAC) as a "Nature/Science" market, had a November top 10 heavily laced with nature and science programming along with music or film retrospectives.

Ratings are usually gathered for programs, although they are also generated for time periods. In public TV, ratings tend to be small (twos, threes and fours). Comparing public and commercial stations' ratings is often a fruitless exercise. One reason for public TV's deficit is its varied and diverse schedule. Network affiliates present a narrow range of sitcoms, action/adventure, soap operas and news. Many indies do merely a mix of off-network reruns, sports, movies and animated kiddy programs. But public TV does instruction, children's programs, science, documentaries, news/talk, culture, dance and music performance, comedy, how-to, contemporary music, film and drama. The hugely varied schedule is public TV's strength and weakness--attracting viewers with diverse interests for a relatively brief amount of time each month.