Frequencies for first 10,000 rows of dgestat variable in natl1987 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          3        0.03        0.03
         18 |          2        0.02        0.05
         19 |          1        0.01        0.06
         20 |          9        0.09        0.15
         21 |          6        0.06        0.21
         22 |          5        0.05        0.26
         23 |          6        0.06        0.32
         24 |         10        0.10        0.42
         25 |         22        0.22        0.64
         26 |         21        0.21        0.85
         27 |         15        0.15        1.00
         28 |         24        0.24        1.24
         29 |         27        0.27        1.51
         30 |         48        0.48        1.99
         31 |         56        0.56        2.55
         32 |         62        0.62        3.17
         33 |        107        1.07        4.24
         34 |        209        2.09        6.33
         35 |        233        2.33        8.66
         36 |        381        3.81       12.47
         37 |        600        6.00       18.47
         38 |      1,082       10.82       29.29
         39 |      1,948       19.48       48.77
         40 |      2,005       20.05       68.82
         41 |      1,253       12.53       81.35
         42 |        715        7.15       88.50
         43 |        311        3.11       91.61
         44 |        210        2.10       93.71
         45 |        126        1.26       94.97
         46 |         73        0.73       95.70
         47 |         48        0.48       96.18
         48 |         26        0.26       96.44
         49 |         21        0.21       96.65
         50 |         13        0.13       96.78
         51 |         17        0.17       96.95
         52 |         10        0.10       97.05
         99 |        295        2.95      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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