Frequencies for first 10,000 rows of clingest variable in natl1997 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         19 |          5        0.05        0.05
         20 |          9        0.09        0.14
         21 |          5        0.05        0.19
         22 |          4        0.04        0.23
         23 |         14        0.14        0.37
         24 |         16        0.16        0.53
         25 |         12        0.12        0.65
         26 |          9        0.09        0.74
         27 |         19        0.19        0.93
         28 |         27        0.27        1.20
         29 |         16        0.16        1.36
         30 |         24        0.24        1.60
         31 |         26        0.26        1.86
         32 |         48        0.48        2.34
         33 |        100        1.00        3.34
         34 |        124        1.24        4.58
         35 |        201        2.01        6.59
         36 |        423        4.23       10.82
         37 |        704        7.04       17.86
         38 |      1,609       16.09       33.95
         39 |      2,430       24.30       58.25
         40 |      3,106       31.06       89.31
         41 |        861        8.61       97.92
         42 |        184        1.84       99.76
         43 |          1        0.01       99.77
         44 |          1        0.01       99.78
         99 |         22        0.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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