Coady, Chan, Auer, Farley, Kilgore, Kansagra (2011)
"Awareness and impact of New York City's graphic point-of-sale tobacco health warning signs"[1] is a research paper that in its conclusion states categorically:
Additional research aimed at evaluating the effect of tobacco control measures in the retail environment is necessary to provide further rationale for implementing these changes and countering legal challenges from the tobacco industry.
Among the major findings we have:
There was no difference across surveys in the signs helping recent quitters to stay quit (p->0.55).
Differences in signs prompting smokers not to purchase cigarettes achieved only borderline significance (15% to 8%, p->0.05).[2]
As pointed out[2] that last effect shows more respondents were less inclined to purchase cigarettes before the posters than after - the complete opposite what is imagined.
In other words, this paper found there was no (or the opposite of the desired) effect on the graphic PoS health warning signs, but still recommends that the policy should continue and further research be carried out to support the policy, since this bit of research failed at doing exactly that. Not quite how research is supposed to be carried out.
Authors