Moving yearly Total Data / month

all values are listed as: MB

   time  |     bcast     bogey
---------+--------------------
2009-01  |   411.949     0.036
2009-02  |   481.435     0.036
2009-03  |   563.186     0.036
2009-04  |   608.421     0.759
2009-05  |   673.604     0.807
2009-06  |   811.958     0.807
2009-07  |   969.902     0.807
2009-08  |  1234.460     0.836
2009-09  |  1335.609     0.812
2009-10  |  1443.017     0.812
2009-11  |  1463.812     0.803
2009-12  |  1460.378     0.803
2010-01  |  1536.732     0.803