Frequencies for first 10,000 rows of gestwk variable in namcs2012 dataset :

Gestation week |      Freq.     Percent        Cum.
---------------+-----------------------------------
         Blank |      5,489       54.89       54.89
       Unknown |          2        0.02       54.91
Not applicable |      4,248       42.48       97.39
             2 |          3        0.03       97.42
             4 |          1        0.01       97.43
             5 |          4        0.04       97.47
             7 |          7        0.07       97.54
             8 |          6        0.06       97.60
             9 |          7        0.07       97.67
            10 |          4        0.04       97.71
            11 |          6        0.06       97.77
            12 |          9        0.09       97.86
            13 |          6        0.06       97.92
            14 |          3        0.03       97.95
            15 |          4        0.04       97.99
            16 |          4        0.04       98.03
            17 |          4        0.04       98.07
            18 |          4        0.04       98.11
            19 |          7        0.07       98.18
            20 |          7        0.07       98.25
            21 |          7        0.07       98.32
            22 |          6        0.06       98.38
            23 |          5        0.05       98.43
            24 |          6        0.06       98.49
            25 |          8        0.08       98.57
            26 |         11        0.11       98.68
            27 |          8        0.08       98.76
            28 |         13        0.13       98.89
            29 |          9        0.09       98.98
            30 |          7        0.07       99.05
            31 |          3        0.03       99.08
            32 |         14        0.14       99.22
            33 |          8        0.08       99.30
            34 |          7        0.07       99.37
            35 |         13        0.13       99.50
            36 |         12        0.12       99.62
            37 |         14        0.14       99.76
            38 |         11        0.11       99.87
            39 |          6        0.06       99.93
            40 |          5        0.05       99.98
            41 |          1        0.01       99.99
            42 |          1        0.01      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016