Frequencies for first 10,000 rows of dgestat variable in natl1976 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          1        0.01        0.01
         18 |          1        0.01        0.02
         19 |          1        0.01        0.03
         20 |          2        0.02        0.05
         21 |          3        0.03        0.08
         22 |          4        0.04        0.12
         23 |          2        0.02        0.14
         24 |          4        0.04        0.18
         25 |          8        0.08        0.26
         26 |          8        0.08        0.34
         27 |         11        0.11        0.45
         28 |         17        0.17        0.62
         29 |         20        0.20        0.82
         30 |         23        0.23        1.05
         31 |         28        0.28        1.33
         32 |         48        0.48        1.81
         33 |         78        0.78        2.59
         34 |        128        1.28        3.87
         35 |        213        2.13        6.00
         36 |        254        2.54        8.54
         37 |        457        4.57       13.11
         38 |        933        9.33       22.44
         39 |      1,608       16.08       38.52
         40 |      1,731       17.31       55.83
         41 |      1,253       12.53       68.36
         42 |        677        6.77       75.13
         43 |        353        3.53       78.66
         44 |        171        1.71       80.37
         45 |        106        1.06       81.43
         46 |         64        0.64       82.07
         47 |         33        0.33       82.40
         48 |         20        0.20       82.60
         49 |         10        0.10       82.70
         50 |          9        0.09       82.79
         51 |          9        0.09       82.88
         52 |          7        0.07       82.95
         99 |      1,705       17.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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