Frequencies for first 10,000 rows of dgestat variable in natl1986 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          1        0.01        0.01
         18 |          2        0.02        0.03
         19 |          4        0.04        0.07
         20 |          3        0.03        0.10
         21 |          3        0.03        0.13
         22 |          3        0.03        0.16
         23 |         10        0.10        0.26
         24 |         10        0.10        0.36
         25 |         14        0.14        0.50
         26 |         18        0.18        0.68
         27 |         20        0.20        0.88
         28 |         28        0.28        1.16
         29 |         29        0.29        1.45
         30 |         32        0.32        1.77
         31 |         46        0.46        2.23
         32 |         71        0.71        2.94
         33 |        101        1.01        3.95
         34 |        123        1.23        5.18
         35 |        208        2.08        7.26
         36 |        378        3.78       11.04
         37 |        581        5.81       16.85
         38 |      1,148       11.48       28.33
         39 |      1,955       19.55       47.88
         40 |      1,973       19.73       67.61
         41 |      1,398       13.98       81.59
         42 |        722        7.22       88.81
         43 |        322        3.22       92.03
         44 |        184        1.84       93.87
         45 |         88        0.88       94.75
         46 |         59        0.59       95.34
         47 |         43        0.43       95.77
         48 |         29        0.29       96.06
         49 |         18        0.18       96.24
         50 |          9        0.09       96.33
         51 |          8        0.08       96.41
         52 |          5        0.05       96.46
         99 |        354        3.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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