Frequencies for first 10,000 rows of birmon variable in natl1988 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,413       44.13       44.13
          2 |      3,548       35.48       79.61
          3 |      1,942       19.42       99.03
          4 |         97        0.97      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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