This surprised me - a dog that wins Best in Show at the Westminster Dog Show doesn't increase the number of new registrations for that breed - for at least five years.
For breeds that had won the Westminster Show, the slope of the curve for number of new registrations per year for the 5 years prior to winning was not significantly different from the slope of the curve for the 5 years after winning. Annual percentage change in number of new registrations for the breed that won each year was not significantly different from annual percentage change in number of new registrations for matched non-winning breeds.
Herzon, H.A. & Elias, S.M. 2004. Effects of winning the Westminster Kennel Club Dog Show on breed popularity. Journal of the American Veterinary Medical Association. 225(3):365-367.
In terms of consumer psychology, winners usually lead to increased sales - but not in this case. I think there could be a few reasons for this:
1. More people are aware of homeless pets and their need for good homes - therefore, less people are buying purebred dogs. However, I don't think purebred dog registrations as a whole have decreased.