Frequencies for first 10,000 rows of gestwk variable in namcs2013 dataset :

Gestation week |      Freq.     Percent        Cum.
---------------+-----------------------------------
         Blank |      5,438       54.38       54.38
       Unknown |          5        0.05       54.43
Not applicable |      4,220       42.20       96.63
             2 |          2        0.02       96.65
             4 |          1        0.01       96.66
             5 |          1        0.01       96.67
             6 |          6        0.06       96.73
             8 |          9        0.09       96.82
             9 |          6        0.06       96.88
            10 |          4        0.04       96.92
            11 |          3        0.03       96.95
            12 |          7        0.07       97.02
            13 |          9        0.09       97.11
            14 |          7        0.07       97.18
            15 |          6        0.06       97.24
            16 |          6        0.06       97.30
            17 |          5        0.05       97.35
            18 |          9        0.09       97.44
            19 |          6        0.06       97.50
            20 |         12        0.12       97.62
            21 |          5        0.05       97.67
            22 |          5        0.05       97.72
            23 |         10        0.10       97.82
            24 |          5        0.05       97.87
            25 |          6        0.06       97.93
            26 |          9        0.09       98.02
            27 |         13        0.13       98.15
            28 |         11        0.11       98.26
            29 |          8        0.08       98.34
            30 |         14        0.14       98.48
            31 |         15        0.15       98.63
            32 |         15        0.15       98.78
            33 |         11        0.11       98.89
            34 |          8        0.08       98.97
            35 |         13        0.13       99.10
            36 |         23        0.23       99.33
            37 |         19        0.19       99.52
            38 |         27        0.27       99.79
            39 |         12        0.12       99.91
            40 |          6        0.06       99.97
            41 |          1        0.01       99.98
            42 |          2        0.02      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 27 Mar 2017