Frequencies for first 10,000 rows of clingest variable in natl1996 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         18 |          1        0.01        0.01
         20 |          4        0.04        0.05
         21 |         17        0.17        0.22
         22 |          2        0.02        0.24
         23 |         17        0.17        0.41
         24 |         14        0.14        0.55
         25 |         13        0.13        0.68
         26 |         19        0.19        0.87
         27 |         20        0.20        1.07
         28 |         24        0.24        1.31
         29 |         19        0.19        1.50
         30 |         23        0.23        1.73
         31 |         22        0.22        1.95
         32 |         62        0.62        2.57
         33 |         82        0.82        3.39
         34 |        145        1.45        4.84
         35 |        179        1.79        6.63
         36 |        402        4.02       10.65
         37 |        757        7.57       18.22
         38 |      1,501       15.01       33.23
         39 |      2,377       23.77       57.00
         40 |      3,182       31.82       88.82
         41 |        916        9.16       97.98
         42 |        174        1.74       99.72
         43 |          7        0.07       99.79
         44 |          1        0.01       99.80
         45 |          1        0.01       99.81
         99 |         19        0.19      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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