Frequencies for first 10,000 rows of dgestat variable in natlterr1999 dataset :

Gestation - |
  Detail in |
      Weeks |      Freq.     Percent        Cum.
------------+-----------------------------------
         20 |          1        0.01        0.01
         21 |          3        0.03        0.04
         22 |          8        0.08        0.12
         23 |          3        0.03        0.15
         24 |          9        0.09        0.24
         25 |         11        0.11        0.35
         26 |         14        0.14        0.49
         27 |         13        0.13        0.62
         28 |         20        0.20        0.82
         29 |         23        0.23        1.05
         30 |         27        0.27        1.32
         31 |         50        0.50        1.82
         32 |         82        0.82        2.64
         33 |        104        1.04        3.68
         34 |        171        1.71        5.39
         35 |        289        2.89        8.28
         36 |        570        5.70       13.98
         37 |      1,219       12.19       26.17
         38 |      2,167       21.67       47.84
         39 |      2,400       24.00       71.84
         40 |      1,909       19.09       90.93
         41 |        623        6.23       97.16
         42 |        184        1.84       99.00
         43 |         83        0.83       99.83
         44 |          9        0.09       99.92
         47 |          1        0.01       99.93
         99 |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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