Frequencies for first 10,000 rows of combgest variable in natl2009 dataset :

Gestation - |
  Detail in |
  Weeks U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         18 |          1        0.01        0.01
         19 |          3        0.03        0.04
         20 |          3        0.03        0.07
         21 |          4        0.04        0.11
         22 |          4        0.04        0.15
         23 |          8        0.08        0.23
         24 |          9        0.09        0.32
         25 |          5        0.05        0.37
         26 |         18        0.18        0.55
         27 |         12        0.12        0.67
         28 |         31        0.31        0.98
         29 |         27        0.27        1.25
         30 |         33        0.33        1.58
         31 |         55        0.55        2.13
         32 |         55        0.55        2.68
         33 |         96        0.96        3.64
         34 |        168        1.68        5.32
         35 |        286        2.86        8.18
         36 |        517        5.17       13.35
         37 |        967        9.67       23.02
         38 |      2,065       20.65       43.67
         39 |      2,726       27.26       70.93
         40 |      1,626       16.26       87.19
         41 |        639        6.39       93.58
         42 |        294        2.94       96.52
         43 |        168        1.68       98.20
         44 |         81        0.81       99.01
         45 |         50        0.50       99.51
         46 |         34        0.34       99.85
         47 |         13        0.13       99.98
         99 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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