Frequencies for first 10,000 rows of combgest variable in natl2011 dataset :

Gestation - |
  Detail in |
  Weeks U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         19 |          1        0.01        0.01
         21 |          1        0.01        0.02
         22 |          4        0.04        0.06
         23 |          2        0.02        0.08
         24 |          5        0.05        0.13
         25 |          8        0.08        0.21
         26 |          4        0.04        0.25
         27 |          9        0.09        0.34
         28 |         12        0.12        0.46
         29 |         19        0.19        0.65
         30 |         25        0.25        0.90
         31 |         40        0.40        1.30
         32 |         55        0.55        1.85
         33 |         74        0.74        2.59
         34 |        147        1.47        4.06
         35 |        213        2.13        6.19
         36 |        394        3.94       10.13
         37 |        862        8.62       18.75
         38 |      1,584       15.84       34.59
         39 |      2,619       26.19       60.78
         40 |      2,244       22.44       83.22
         41 |      1,066       10.66       93.88
         42 |        280        2.80       96.68
         43 |        156        1.56       98.24
         44 |         69        0.69       98.93
         45 |         39        0.39       99.32
         46 |         29        0.29       99.61
         47 |         16        0.16       99.77
         99 |         23        0.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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