Frequencies for first 10,000 rows of estgest variable in natl2005 dataset :

Obstetric/C |
    linical |
  Gestation |
   Est. U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          1        0.01        0.01
         18 |          2        0.02        0.03
         20 |          2        0.02        0.05
         22 |          8        0.08        0.13
         23 |          5        0.05        0.18
         24 |          4        0.04        0.22
         25 |          4        0.04        0.26
         26 |          8        0.08        0.34
         27 |          7        0.07        0.41
         28 |         12        0.12        0.53
         29 |         12        0.12        0.65
         30 |         25        0.25        0.90
         31 |         21        0.21        1.11
         32 |         31        0.31        1.42
         33 |         62        0.62        2.04
         34 |        114        1.14        3.18
         35 |        174        1.74        4.92
         36 |        369        3.69        8.61
         37 |        775        7.75       16.36
         38 |      1,687       16.87       33.23
         39 |      2,742       27.42       60.65
         40 |      2,792       27.92       88.57
         41 |      1,026       10.26       98.83
         42 |         93        0.93       99.76
         43 |          1        0.01       99.77
         44 |          1        0.01       99.78
         45 |          1        0.01       99.79
         99 |         21        0.21      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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