Frequencies for first 10,000 rows of clingest variable in natl2001 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         18 |          1        0.01        0.01
         19 |          1        0.01        0.02
         20 |          4        0.04        0.06
         21 |          7        0.07        0.13
         22 |          4        0.04        0.17
         23 |         12        0.12        0.29
         24 |         15        0.15        0.44
         25 |         12        0.12        0.56
         26 |         10        0.10        0.66
         27 |         27        0.27        0.93
         28 |         20        0.20        1.13
         29 |         26        0.26        1.39
         30 |         26        0.26        1.65
         31 |         26        0.26        1.91
         32 |         62        0.62        2.53
         33 |         88        0.88        3.41
         34 |        113        1.13        4.54
         35 |        234        2.34        6.88
         36 |        482        4.82       11.70
         37 |        897        8.97       20.67
         38 |      2,035       20.35       41.02
         39 |      2,771       27.71       68.73
         40 |      2,417       24.17       92.90
         41 |        623        6.23       99.13
         42 |         72        0.72       99.85
         99 |         15        0.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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