Frequencies for first 10,000 rows of dmage variable in natl1987 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         10 |          1        0.01        0.01
         12 |          2        0.02        0.03
         13 |         14        0.14        0.17
         14 |         53        0.53        0.70
         15 |        130        1.30        2.00
         16 |        249        2.49        4.49
         17 |        382        3.82        8.31
         18 |        475        4.75       13.06
         19 |        595        5.95       19.01
         20 |        636        6.36       25.37
         21 |        612        6.12       31.49
         22 |        685        6.85       38.34
         23 |        637        6.37       44.71
         24 |        657        6.57       51.28
         25 |        648        6.48       57.76
         26 |        640        6.40       64.16
         27 |        586        5.86       70.02
         28 |        531        5.31       75.33
         29 |        518        5.18       80.51
         30 |        430        4.30       84.81
         31 |        351        3.51       88.32
         32 |        259        2.59       90.91
         33 |        238        2.38       93.29
         34 |        177        1.77       95.06
         35 |        149        1.49       96.55
         36 |        111        1.11       97.66
         37 |         81        0.81       98.47
         38 |         61        0.61       99.08
         39 |         45        0.45       99.53
         40 |         22        0.22       99.75
         41 |         11        0.11       99.86
         42 |          6        0.06       99.92
         43 |          5        0.05       99.97
         44 |          2        0.02       99.99
         48 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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