Frequencies for first 10,000 rows of dgestat variable in natl1988 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          2        0.02        0.02
         18 |          1        0.01        0.03
         19 |          3        0.03        0.06
         20 |         11        0.11        0.17
         21 |          2        0.02        0.19
         22 |         12        0.12        0.31
         23 |          9        0.09        0.40
         24 |          9        0.09        0.49
         25 |         14        0.14        0.63
         26 |         21        0.21        0.84
         27 |         27        0.27        1.11
         28 |         20        0.20        1.31
         29 |         29        0.29        1.60
         30 |         51        0.51        2.11
         31 |         49        0.49        2.60
         32 |         88        0.88        3.48
         33 |         81        0.81        4.29
         34 |        173        1.73        6.02
         35 |        226        2.26        8.28
         36 |        353        3.53       11.81
         37 |        604        6.04       17.85
         38 |      1,149       11.49       29.34
         39 |      1,947       19.47       48.81
         40 |      2,025       20.25       69.06
         41 |      1,292       12.92       81.98
         42 |        647        6.47       88.45
         43 |        341        3.41       91.86
         44 |        210        2.10       93.96
         45 |         97        0.97       94.93
         46 |         66        0.66       95.59
         47 |         37        0.37       95.96
         48 |         39        0.39       96.35
         49 |         18        0.18       96.53
         50 |          8        0.08       96.61
         51 |          8        0.08       96.69
         52 |          9        0.09       96.78
         99 |        322        3.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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