I’ve found the problem. Craigslist changed the way they do searches sometime between July 4 and July 11. It used to be the search for “kittens” did not include ads that only used the singular “kitten”, but now it does, so the numbers are higher.
That means I can’t learn anything by comparing new data to all the lovely stuff I’ve been collecting since 2009.
Well, at least there isn’t the population explosion I feared. One warm winter didn’t undo the progress made from years of spay/neuter. *whew* My data on places like Eugene, Springfield and Salem show what s/n can do.