Frequencies for first 10,000 rows of dmage variable in natl1981 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         12 |          2        0.02        0.02
         13 |          8        0.08        0.10
         14 |         34        0.34        0.44
         15 |        124        1.24        1.68
         16 |        290        2.90        4.58
         17 |        411        4.11        8.69
         18 |        529        5.29       13.98
         19 |        637        6.37       20.35
         20 |        698        6.98       27.33
         21 |        727        7.27       34.60
         22 |        719        7.19       41.79
         23 |        723        7.23       49.02
         24 |        670        6.70       55.72
         25 |        646        6.46       62.18
         26 |        670        6.70       68.88
         27 |        580        5.80       74.68
         28 |        517        5.17       79.85
         29 |        404        4.04       83.89
         30 |        354        3.54       87.43
         31 |        313        3.13       90.56
         32 |        218        2.18       92.74
         33 |        183        1.83       94.57
         34 |        147        1.47       96.04
         35 |         89        0.89       96.93
         36 |         85        0.85       97.78
         37 |         72        0.72       98.50
         38 |         49        0.49       98.99
         39 |         31        0.31       99.30
         40 |         26        0.26       99.56
         41 |         13        0.13       99.69
         42 |         14        0.14       99.83
         43 |          7        0.07       99.90
         44 |          3        0.03       99.93
         45 |          4        0.04       99.97
         46 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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