Frequencies for first 10,000 rows of estgest variable in natl2003 dataset :

Obstetric/C |
    linical |
  Gestation |
   Est. U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         20 |          1        0.01        0.01
         21 |          1        0.01        0.02
         22 |          3        0.03        0.05
         23 |          5        0.05        0.10
         24 |          4        0.04        0.14
         25 |          7        0.07        0.21
         26 |         13        0.13        0.34
         27 |          4        0.04        0.38
         28 |         16        0.16        0.54
         29 |         16        0.16        0.70
         30 |         19        0.19        0.89
         31 |         23        0.23        1.12
         32 |         42        0.42        1.54
         33 |         57        0.57        2.11
         34 |        112        1.12        3.23
         35 |        181        1.81        5.04
         36 |        428        4.28        9.32
         37 |        732        7.32       16.64
         38 |      1,607       16.07       32.71
         39 |      2,481       24.81       57.52
         40 |      2,840       28.40       85.92
         41 |      1,083       10.83       96.75
         42 |        174        1.74       98.49
         43 |          4        0.04       98.53
         44 |          2        0.02       98.55
         47 |          1        0.01       98.56
         99 |        144        1.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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