For the moment, let us take the more restrictive meaning - just puppies born in the United States. There are approximately 400 Norwich born each year in the United States. Sadly this number seems to be in decline (484 puppies in 2013, 375 puppies in 2017). So five percent would be 20 puppies. The average Norwich litter size is 2.7 puppies. So then a Norwich popular sire would be one that produces 7 or 8 litters over a five year period - which is probably the length of a stud dog's breeding career.
I do not have any good statistics on the number of Norwich born in a year in the world. But a reasonable guess is double the number born in the United States. Using that figure, that would mean that a Norwich popular sire would be one that produces 14 or 15 litters over its breeding career.
Some time ago, I used my pedigree database to calculate Norwich popular sires. I used the figure of 10 litters as my definition of a Norwich popular sire. You can see the results by going to my online Norwich pedigree database clicking on "Statistics" (at the bottom), then on the next page clicking "Popular Sires Report" (again at the bottom of the page). Updating this report is on my "to do" list.
23 Nov 2020