Frequencies for first 10,000 rows of gestat10 variable in natl1981 dataset :

  Gestation |
  Recode 10 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          3        0.03        0.03
          2 |         63        0.63        0.66
          3 |        136        1.36        2.02
          4 |        551        5.51        7.53
          5 |        351        3.51       11.04
          6 |      3,518       35.18       46.22
          7 |      2,137       21.37       67.59
          8 |      1,443       14.43       82.02
          9 |      1,583       15.83       97.85
         10 |        215        2.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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