Frequencies for first 10,000 rows of dmage variable in natl1973 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         12 |          4        0.04        0.04
         13 |         11        0.11        0.15
         14 |         63        0.63        0.78
         15 |        209        2.09        2.87
         16 |        383        3.83        6.70
         17 |        561        5.61       12.31
         18 |        726        7.26       19.57
         19 |        824        8.24       27.81
         20 |        715        7.15       34.96
         21 |        741        7.41       42.37
         22 |        713        7.13       49.50
         23 |        669        6.69       56.19
         24 |        633        6.33       62.52
         25 |        667        6.67       69.19
         26 |        572        5.72       74.91
         27 |        387        3.87       78.78
         28 |        360        3.60       82.38
         29 |        330        3.30       85.68
         30 |        262        2.62       88.30
         31 |        196        1.96       90.26
         32 |        172        1.72       91.98
         33 |        157        1.57       93.55
         34 |        138        1.38       94.93
         35 |        109        1.09       96.02
         36 |         81        0.81       96.83
         37 |         87        0.87       97.70
         38 |         62        0.62       98.32
         39 |         57        0.57       98.89
         40 |         39        0.39       99.28
         41 |         23        0.23       99.51
         42 |         22        0.22       99.73
         43 |         16        0.16       99.89
         44 |          6        0.06       99.95
         45 |          2        0.02       99.97
         46 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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