Analysis report for common sense in media ~ A-time share%

SPI reported on the analysis for “common sense in media”, to reconsider the “significant point”.

This time we focused on “A-time share%” , which is normally regarded as important when buying TV media.

*Definition of “A-time share%”
A-time is called “Prime-time” in general, which is around 7~11pm, the highest TV-rating zone of the day.
A-time share% is calculated by A-time GRP / Total GRP.
**Note; TVCM on air day & time is difficult to control in the case of TVSpot (NOT Sponsored programs) in Japan (Not like in the US or western Europe).


*Why is there a time rank?
There was no reliable TV-rating when TVCM when buying started, therefore, TVCM purchasing was based on the number of CM (=Spot) bases, however, its prices are ranked by timezone (to reflect its value).

*Contradiction in buying the TVSpot based on GRP
Almost of the advertisers buy TVSpot by GRP base referring to TV-rating (higher TV-rating zone becomes higher buying-costs), therefore, time rank seems to have lost its significance.
Therefore, SPI analyzes the significance of A-time share% in TVSpot buying.

1, Conversion ratio of Individual-rating
GRP should be based on the “Household-rating” in Japan when buying a TVSpot.
The “Household” rating in A-time has a much more “Individual-rating”, therefore GRP in A-time is much more important than GRP in other zones. 201403_2.png

2, reach expansion
GRP is the Gross Rating Point, therefore, you can say that 2GRP means “the same person might have watched twice”.
Therefore, getting higher GRP with a CM is better in expanding reach compared with less GRP.
For example (as a possibility);
*2 GRP by 1 CM = 2 people watch once >>>reaches 2 people
**2 GRP by 2 CM = 1 people watch 2 times >>>reaches 1 person

3, impact
SPI found the possibility that a TVCM in A-time has more impact than in other zones, because the quality of TV-watching then might be better than during other times.
There is the comparison of TV-ratings between “machine-based = VR (TV-rating is counted by channel on/off)” and “questionnaire based = SPI (TV-rating is counted by samples’ answers)”.

This analysis illustrates “machine-based = VR (TV-rating is counted by channel on/off)” is lower than the “questionnaire based = SPI (TV-rating is counted by sample’s answer)”. We see there is a possibility that A-time TV programs have better condition audience viewing conditions.

From these reasons, SPI understands that A-time share% is important in improving TVSpot performance.


Shiro Kokue
Senior consultant

Please contact us with questions or for more detailed information.


  • This report and its contents are NOT officially guaranteed by SPI, though SPI may deem it worthy according to reliable information, resources & methodology.
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