Dog registration is not required but is a great idea to get your new puppy or adult dog registered if your breeder has not already done so. (animaroo.com)
However, that's a list of dogs registered with the AKC — records from the New York City Department of Health and Mental Hygiene, the city agency that runs the dog licensing program, say the five most popular breeds are: (urbandognyc.com)
A Danish study conducted in 2010 researched litter size for 224 breeds of dogs registered in the Norwegian Kennel Club between January 1, 2006 and December 31, 2007 and found that the average litter size was 5.5. (breedingbusiness.com)