Frequencies for first 10,000 rows of dmage variable in natl1990 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         13 |          5        0.05        0.05
         14 |         41        0.41        0.46
         15 |        107        1.07        1.53
         16 |        220        2.20        3.73
         17 |        371        3.71        7.44
         18 |        519        5.19       12.63
         19 |        623        6.23       18.86
         20 |        602        6.02       24.88
         21 |        638        6.38       31.26
         22 |        604        6.04       37.30
         23 |        637        6.37       43.67
         24 |        636        6.36       50.03
         25 |        614        6.14       56.17
         26 |        619        6.19       62.36
         27 |        572        5.72       68.08
         28 |        553        5.53       73.61
         29 |        504        5.04       78.65
         30 |        440        4.40       83.05
         31 |        349        3.49       86.54
         32 |        312        3.12       89.66
         33 |        256        2.56       92.22
         34 |        198        1.98       94.20
         35 |        186        1.86       96.06
         36 |        125        1.25       97.31
         37 |         98        0.98       98.29
         38 |         67        0.67       98.96
         39 |         34        0.34       99.30
         40 |         33        0.33       99.63
         41 |         18        0.18       99.81
         42 |         11        0.11       99.92
         43 |          5        0.05       99.97
         44 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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