When we started the California Correctional Crisis blog in 2008, we opened with a post linking to this story from NPR, and included an image of makeshift beds in the gym. Would you believe then that you would be seeing images like the one on the left?
CDCR has published a series of images on Flickr showing decrowded facilities. Do watch the whole slideshow. While these are not quantitative data, they are, indeed, powerful; the before-and-after shots are particularly striking, though I'd be more impressed if they were properly labeled and depicted the exact same locations. For the actual numbers you'll have to wait three days; December 27th is the first court-mandated benchmark for monitoring the progress of population reduction ordered in Brown v. Plata. And, of course, the CCC blog will accompany you then and comment on the state's progress in decrowding its prisons.