It's not really possible to give an exact number for how many Nihon Ken were actually born and registered in Japan for any given year. The reason for this is that there are dual registrations (ie none of the 20 JKC registered Shikoku were actually JKC bred. They are transfers from NIPPO), and some of the registries allow registration of pups born overseas (NIPPO, KKA, AKIHO), and those totals are included in the registry total. But these numbers give us a general idea of where the breeds are headed. It's a sad day for the Shikoku, as last year less than 200 were born in Japan (I know that more than 20 of the registered pups were born overseas). This means the breed continues to hold the dubious distinction of being the rarest of the 6 Nihon Ken (in Japan anyway).
Shiba (NIPPO) 27,300 (JKC) 9,262
Akita (AKIHO) 3323 (JKC) 258
Kai (KKA) 914 (NIPPO) 87 (JKC) 93
Hokkaido (HKH) 222 (HKK) 67 (JKC) 25 (NIPPO) 12
Kishu (NIPPO) 265 (JKC) 1
Shikoku (NIPPO) 219 (JKC) 20
