Frequencies for first 10,000 rows of birmon variable in natl1972 dataset :

   Month of |
      birth |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,676       26.76       26.76
          2 |      2,523       25.23       51.99
          3 |      2,430       24.30       76.29
          4 |      1,912       19.12       95.41
          5 |        459        4.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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