Frequencies for first 10,000 rows of birmon variable in natl1969 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,673       26.73       26.73
          2 |      2,399       23.99       50.72
          3 |      2,492       24.92       75.64
          4 |      2,008       20.08       95.72
          5 |        426        4.26       99.98
          6 |          1        0.01       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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