Seems like a few months ago that the way newspapers calculated circulation numbers was under attack from their financial backers. Could this be an adjustment resulting from that criticism or has that adjustment already taken place?
You might be right for some of the papers that took the biggest hits -- dropping 16% in that small a period of time seems unlikely. Especially in an overwhelmingly liberal city. I doubt there are many conservatives in open rebellion against the newspaper in San Francisco. Still, it's possible. Who knows.
I'm amazed newspapers would stonewall conservatives to the point of going out of business ... but they are. Strange world.