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

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          1        0.01        0.01
         18 |          1        0.01        0.02
         19 |          1        0.01        0.03
         20 |          1        0.01        0.04
         21 |          6        0.06        0.10
         22 |          6        0.06        0.16
         23 |          9        0.09        0.25
         24 |          6        0.06        0.31
         25 |         10        0.10        0.41
         26 |          7        0.07        0.48
         27 |         18        0.18        0.66
         28 |         19        0.19        0.85
         29 |         35        0.35        1.20
         30 |         32        0.32        1.52
         31 |         50        0.50        2.02
         32 |         63        0.63        2.65
         33 |         95        0.95        3.60
         34 |        159        1.59        5.19
         35 |        234        2.34        7.53
         36 |        351        3.51       11.04
         37 |        573        5.73       16.77
         38 |      1,112       11.12       27.89
         39 |      1,833       18.33       46.22
         40 |      2,137       21.37       67.59
         41 |      1,443       14.43       82.02
         42 |        771        7.71       89.73
         43 |        369        3.69       93.42
         44 |        184        1.84       95.26
         45 |        121        1.21       96.47
         46 |         58        0.58       97.05
         47 |         41        0.41       97.46
         48 |         19        0.19       97.65
         49 |         11        0.11       97.76
         50 |          3        0.03       97.79
         51 |          2        0.02       97.81
         52 |          4        0.04       97.85
         99 |        215        2.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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