Frequencies for first 10,000 rows of birmon variable in natl1985 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,796       47.96       47.96
          2 |      3,640       36.40       84.36
          3 |      1,563       15.63       99.99
         11 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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