Frequencies for first 10,000 rows of clingest variable in natl1990 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         20 |          1        0.01        0.01
         21 |          1        0.01        0.02
         22 |          9        0.09        0.11
         23 |         11        0.11        0.22
         24 |          9        0.09        0.31
         25 |          9        0.09        0.40
         26 |         13        0.13        0.53
         27 |         11        0.11        0.64
         28 |         22        0.22        0.86
         29 |         15        0.15        1.01
         30 |         25        0.25        1.26
         31 |         36        0.36        1.62
         32 |         49        0.49        2.11
         33 |         48        0.48        2.59
         34 |        106        1.06        3.65
         35 |        170        1.70        5.35
         36 |        370        3.70        9.05
         37 |        561        5.61       14.66
         38 |      1,359       13.59       28.25
         39 |      1,948       19.48       47.73
         40 |      3,593       35.93       83.66
         41 |      1,101       11.01       94.67
         42 |        414        4.14       98.81
         43 |         47        0.47       99.28
         44 |          6        0.06       99.34
         99 |         66        0.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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