From The Grocer, 3 November 2007:
'[There has been] a drop in pet ownership from 55% of shoppers in 1992 to 44% this year, according to British Market Bureau figures. Dog ownership has been particularly hard hit, falling from 28% to 20%. Cats are now the most popular pet, though ownership has dropped from 24% to 22%'.
The article doesn't analyse the number of cats each shopper is shopping for, but I thought it worth mentioning in passing.