Frequencies for first 10,000 rows of birmon variable in linkco1991us_num dataset :

   Month of |
      Birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        760        7.60        7.60
          2 |        771        7.71       15.31
          3 |        774        7.74       23.05
          4 |        780        7.80       30.85
          5 |        830        8.30       39.15
          6 |        846        8.46       47.61
          7 |        917        9.17       56.78
          8 |        897        8.97       65.75
          9 |        891        8.91       74.66
         10 |        877        8.77       83.43
         11 |        819        8.19       91.62
         12 |        838        8.38      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015