Frequencies for first 10,000 rows of birmon variable in natl1973 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,494       24.94       24.94
          2 |      2,365       23.65       48.59
          3 |      2,443       24.43       73.02
          4 |      2,090       20.90       93.92
          5 |        607        6.07       99.99
         10 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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