Moving yearly Total Data / month

all values are listed as: TB

   time  |  total
---------+-------
2009-01  |  0.669
2009-02  |  0.852
2009-03  |  0.979
2009-04  |  1.184
2009-05  |  1.406
2009-06  |  1.621
2009-07  |  1.838
2009-08  |  2.045
2009-09  |  2.114
2009-10  |  2.079
2009-11  |  2.142
2009-12  |  2.112
2010-01  |  2.083