Frequencies for first 10,000 rows of combgest variable in natl2004 dataset :

Gestation - |
  Detail in |
  Weeks U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         19 |          1        0.01        0.01
         20 |          2        0.02        0.03
         21 |          2        0.02        0.05
         22 |          7        0.07        0.12
         23 |         10        0.10        0.22
         24 |          7        0.07        0.29
         25 |         13        0.13        0.42
         26 |          8        0.08        0.50
         27 |         18        0.18        0.68
         28 |         11        0.11        0.79
         29 |         18        0.18        0.97
         30 |         25        0.25        1.22
         31 |         34        0.34        1.56
         32 |         43        0.43        1.99
         33 |         67        0.67        2.66
         34 |        135        1.35        4.01
         35 |        227        2.27        6.28
         36 |        411        4.11       10.39
         37 |        836        8.36       18.75
         38 |      1,813       18.13       36.88
         39 |      2,487       24.87       61.75
         40 |      2,148       21.48       83.23
         41 |      1,085       10.85       94.08
         42 |        311        3.11       97.19
         43 |        134        1.34       98.53
         44 |         49        0.49       99.02
         45 |         31        0.31       99.33
         46 |         18        0.18       99.51
         47 |         11        0.11       99.62
         99 |         38        0.38      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 21 Jan 2016