Frequencies for first 10,000 rows of dmage variable in natl1989 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         13 |          4        0.04        0.04
         14 |         42        0.42        0.46
         15 |        112        1.12        1.58
         16 |        220        2.20        3.78
         17 |        396        3.96        7.74
         18 |        498        4.98       12.72
         19 |        570        5.70       18.42
         20 |        612        6.12       24.54
         21 |        634        6.34       30.88
         22 |        610        6.10       36.98
         23 |        591        5.91       42.89
         24 |        664        6.64       49.53
         25 |        654        6.54       56.07
         26 |        647        6.47       62.54
         27 |        568        5.68       68.22
         28 |        550        5.50       73.72
         29 |        454        4.54       78.26
         30 |        411        4.11       82.37
         31 |        370        3.70       86.07
         32 |        286        2.86       88.93
         33 |        257        2.57       91.50
         34 |        260        2.60       94.10
         35 |        170        1.70       95.80
         36 |        146        1.46       97.26
         37 |         87        0.87       98.13
         38 |         52        0.52       98.65
         39 |         45        0.45       99.10
         40 |         36        0.36       99.46
         41 |         22        0.22       99.68
         42 |         19        0.19       99.87
         43 |          4        0.04       99.91
         44 |          5        0.05       99.96
         45 |          2        0.02       99.98
         46 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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