Frequencies for first 10,000 rows of combgest variable in natl2008 dataset :

Gestation - |
  Detail in |
  Weeks U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          1        0.01        0.01
         18 |          1        0.01        0.02
         19 |          3        0.03        0.05
         20 |          3        0.03        0.08
         21 |          6        0.06        0.14
         22 |          5        0.05        0.19
         23 |          9        0.09        0.28
         24 |         19        0.19        0.47
         25 |         17        0.17        0.64
         26 |         28        0.28        0.92
         27 |         24        0.24        1.16
         28 |         28        0.28        1.44
         29 |         45        0.45        1.89
         30 |         38        0.38        2.27
         31 |         64        0.64        2.91
         32 |        115        1.15        4.06
         33 |        135        1.35        5.41
         34 |        198        1.98        7.39
         35 |        352        3.52       10.91
         36 |        553        5.53       16.44
         37 |      1,143       11.43       27.87
         38 |      2,191       21.91       49.78
         39 |      2,417       24.17       73.95
         40 |      1,376       13.76       87.71
         41 |        599        5.99       93.70
         42 |        273        2.73       96.43
         43 |        144        1.44       97.87
         44 |         85        0.85       98.72
         45 |         60        0.60       99.32
         46 |         37        0.37       99.69
         47 |         23        0.23       99.92
         99 |          8        0.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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