Frequencies for first 10,000 rows of dmage variable in natl1970 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         11 |          1        0.01        0.01
         12 |          2        0.02        0.03
         13 |         14        0.14        0.17
         14 |         40        0.40        0.57
         15 |        150        1.50        2.07
         16 |        303        3.03        5.10
         17 |        457        4.57        9.67
         18 |        657        6.57       16.24
         19 |        779        7.79       24.03
         20 |        831        8.31       32.34
         21 |        841        8.41       40.75
         22 |        815        8.15       48.90
         23 |        757        7.57       56.47
         24 |        546        5.46       61.93
         25 |        572        5.72       67.65
         26 |        515        5.15       72.80
         27 |        475        4.75       77.55
         28 |        337        3.37       80.92
         29 |        301        3.01       83.93
         30 |        279        2.79       86.72
         31 |        208        2.08       88.80
         32 |        200        2.00       90.80
         33 |        152        1.52       92.32
         34 |        141        1.41       93.73
         35 |        118        1.18       94.91
         36 |        100        1.00       95.91
         37 |        111        1.11       97.02
         38 |         89        0.89       97.91
         39 |         61        0.61       98.52
         40 |         63        0.63       99.15
         41 |         32        0.32       99.47
         42 |         26        0.26       99.73
         43 |         10        0.10       99.83
         44 |          8        0.08       99.91
         45 |          5        0.05       99.96
         46 |          3        0.03       99.99
         47 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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