Frequencies for first 10,000 rows of birmon variable in natl1975 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,451       24.51       24.51
          2 |      2,154       21.54       46.05
          3 |      2,379       23.79       69.84
          4 |      2,184       21.84       91.68
          5 |        831        8.31       99.99
          6 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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