Frequencies for first 10,000 rows of birmon variable in natl1978 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,811       48.11       48.11
          2 |      3,838       38.38       86.49
          3 |      1,351       13.51      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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