Frequencies for first 10,000 rows of birmon variable in natl1987 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,879       48.79       48.79
          2 |      3,576       35.76       84.55
          3 |      1,545       15.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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