The official statistics from DOJ's Bureau of Justice Statistics are out for 2006, with some interesting findings.  "During 2006, the prison population grew at a faster rate than in the previous 5 years...However, the 2006 growth rate was less than the annual growth rates of between 3.4% and 8.7% that occurred during the 1990s..."  The report also includes statistics regarding inmates held in local jails.