Frequencies for first 10,000 rows of birmon variable in natl1970 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,776       27.76       27.76
          2 |      2,538       25.38       53.14
          3 |      2,563       25.63       78.77
          4 |      1,917       19.17       97.94
          5 |        204        2.04       99.98
          6 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016