Frequencies for first 10,000 rows of birmon variable in natl1981 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,977       49.77       49.77
          2 |      3,556       35.56       85.33
          3 |      1,467       14.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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