Frequencies for first 10,000 rows of gestat variable in linkco1991us_num dataset :

Gestation - |
  Detail in |
      Weeks |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |         38        0.38        0.38
         18 |         65        0.65        1.03
         19 |        127        1.27        2.30
         20 |        263        2.63        4.93
         21 |        412        4.12        9.05
         22 |        513        5.13       14.18
         23 |        591        5.91       20.09
         24 |        570        5.70       25.79
         25 |        415        4.15       29.94
         26 |        405        4.05       33.99
         27 |        280        2.80       36.79
         28 |        254        2.54       39.33
         29 |        215        2.15       41.48
         30 |        190        1.90       43.38
         31 |        196        1.96       45.34
         32 |        191        1.91       47.25
         33 |        216        2.16       49.41
         34 |        260        2.60       52.01
         35 |        301        3.01       55.02
         36 |        344        3.44       58.46
         37 |        467        4.67       63.13
         38 |        661        6.61       69.74
         39 |        788        7.88       77.62
         40 |        716        7.16       84.78
         41 |        465        4.65       89.43
         42 |        235        2.35       91.78
         43 |        103        1.03       92.81
         44 |         65        0.65       93.46
         45 |         27        0.27       93.73
         46 |         16        0.16       93.89
         47 |         16        0.16       94.05
         99 |        595        5.95      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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