In [27]:
cohorts[0]
Out[27]:
FirstOrder
2009-01     22.0
2009-02     15.0
2009-03     13.0
2009-04     39.0
2009-05     50.0
2009-06     32.0
2009-07     50.0
2009-08     31.0
2009-09     37.0
2009-10     54.0
2009-11    130.0
2009-12     65.0
2010-01     95.0
2010-02    100.0
2010-03     24.0
Name: 0, dtype: float64