How Do Ratings Affect Reach?
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For a given daypart and network, how does the rating affect reach? Is it necessary to revise ratings in TView to set a precise rating? |
If the definition of the daypart hasn't changed, then modest changes in ratings are unlikely to make much or a difference.
Here's a little exploration that demonstrates the point. We added two "write in" lines into a plansheet, and specified that 100 GRPs would produce a reach of 25.5. (This is consistent with what we might expect for daytime network.) But on one line we specified a rating of 0.46 and on the other line we entered a rating of 0.8. Going to the "Lines" panel on the Details tab, here's the plot of the two reach curves produced by these two write-in entries:
The curve for the vehicle with the 0.8 rating is marked with "+", and the one with the 0.46 rating is marked with "x". Now, if you only see a single line that is marked with "*", well, that's kind of the point! A moderate change in rating really doesn't affect the reach, all else being the same. And since it doesn't make a difference, there is no need to revise it.
But we do see significant changes when the very definition of a vehicle has changed. Changes like these can make a difference in both ratings and reach. Examples:
| • | If "Cable Prime" is defined as TNT, USA and FX, the ratings, cume potential and reach will all be higher than if it's defined as DIY, CNN, and HRTV. |
| • | A Thursday Daytime for a single week will have much higher scores for ratings, cume and reach if that day happens to be Thanksgiving. |
| • | Ratings for C3 will be different than ratings for All Minute Live. |
| • | Defining morning as Mon-Sun 6-9am is different than Mon-Fri 6-10am |
Those kinds of situations are best handled by addressing the definitions, not by tweaking ratings.
By the way, in some cases, if you show an estimated rating in TView it may not match the "official" rating you might get from Nielsen. There are a host of technical reasons for that, including:
| • | analysis for reach and cumes always ignores visitors (at least in the audience system used by U.S. Nielsen) |
| • | Nielsen uses a different system of weights if the purpose is to report ratings or if it's to calculate reach |
| • | unification (or equivalent) to find a group from which to do reach |
In all of those cases, we're talking about the same core definition of a vehicle, so while there may be some differences in ratings calculations, the pattern of audience accumulation for a given GRP level is the same.