score:3
The DoJ published this paper in December 2011 and released prison statistics for 2010. According to the article the number of people in prison at year-end'10 was 7.1 million of which 2,226,800 people were sentenced in 2010 itself [table 1, in that paper].
This wikipedia article also has a lot of detail on this subject. I think you can extrapolate the figures in the DoJ article with the 2011 rates mentioned in the wikipedia article and compute the number of people in Jail in 2011.