Frequencies for first 10,000 rows of birmon variable in natl1977 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,921       49.21       49.21
          2 |      3,859       38.59       87.80
          3 |      1,220       12.20      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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