Frequencies for first 10,000 rows of dmage variable in natl1975 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         11 |          1        0.01        0.01
         12 |          3        0.03        0.04
         13 |         12        0.12        0.16
         14 |         53        0.53        0.69
         15 |        198        1.98        2.67
         16 |        409        4.09        6.76
         17 |        551        5.51       12.27
         18 |        658        6.58       18.85
         19 |        764        7.64       26.49
         20 |        772        7.72       34.21
         21 |        762        7.62       41.83
         22 |        686        6.86       48.69
         23 |        714        7.14       55.83
         24 |        641        6.41       62.24
         25 |        613        6.13       68.37
         26 |        575        5.75       74.12
         27 |        539        5.39       79.51
         28 |        419        4.19       83.70
         29 |        295        2.95       86.65
         30 |        250        2.50       89.15
         31 |        233        2.33       91.48
         32 |        200        2.00       93.48
         33 |        126        1.26       94.74
         34 |        122        1.22       95.96
         35 |         88        0.88       96.84
         36 |         66        0.66       97.50
         37 |         66        0.66       98.16
         38 |         59        0.59       98.75
         39 |         35        0.35       99.10
         40 |         38        0.38       99.48
         41 |         20        0.20       99.68
         42 |         15        0.15       99.83
         43 |          5        0.05       99.88
         44 |          7        0.07       99.95
         45 |          2        0.02       99.97
         46 |          2        0.02       99.99
         47 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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