The unemployment rate for blacks fell more than 2 percentage points last month to its lowest level since March 2009. The drop puzzled economists, who cautioned that it's too early to say that a job market recovery for blacks is underway. The rate for African-Americans didn't budge at all in 2011, ending the year at 15.8%. The overall unemployment rate fell nearly a percentage point last year. But even at 13.6% for January, the unemployment rate for blacks is still far higher than the rate for other racial and ethnic groups, as well as the nation as a whole…