Frequencies for first 10,000 rows of combgest variable in natl2010 dataset :

Gestation - |
  Detail in |
  Weeks U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         20 |          1        0.01        0.01
         21 |          2        0.02        0.03
         22 |          2        0.02        0.05
         23 |          3        0.03        0.08
         24 |          5        0.05        0.13
         25 |          6        0.06        0.19
         26 |          7        0.07        0.26
         27 |         12        0.12        0.38
         28 |         16        0.16        0.54
         29 |         13        0.13        0.67
         30 |         27        0.27        0.94
         31 |         30        0.30        1.24
         32 |         46        0.46        1.70
         33 |         52        0.52        2.22
         34 |        142        1.42        3.64
         35 |        213        2.13        5.77
         36 |        368        3.68        9.45
         37 |        826        8.26       17.71
         38 |      1,666       16.66       34.37
         39 |      2,603       26.03       60.40
         40 |      2,143       21.43       81.83
         41 |      1,109       11.09       92.92
         42 |        387        3.87       96.79
         43 |        151        1.51       98.30
         44 |         73        0.73       99.03
         45 |         42        0.42       99.45
         46 |         18        0.18       99.63
         47 |         16        0.16       99.79
         99 |         21        0.21      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015