Frequencies for first 10,000 rows of dmage variable in natl2000 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         13 |          7        0.07        0.07
         14 |         31        0.31        0.38
         15 |         90        0.90        1.28
         16 |        179        1.79        3.07
         17 |        312        3.12        6.19
         18 |        431        4.31       10.50
         19 |        582        5.82       16.32
         20 |        647        6.47       22.79
         21 |        649        6.49       29.28
         22 |        649        6.49       35.77
         23 |        600        6.00       41.77
         24 |        569        5.69       47.46
         25 |        538        5.38       52.84
         26 |        568        5.68       58.52
         27 |        567        5.67       64.19
         28 |        520        5.20       69.39
         29 |        552        5.52       74.91
         30 |        417        4.17       79.08
         31 |        337        3.37       82.45
         32 |        334        3.34       85.79
         33 |        288        2.88       88.67
         34 |        255        2.55       91.22
         35 |        244        2.44       93.66
         36 |        169        1.69       95.35
         37 |        132        1.32       96.67
         38 |        113        1.13       97.80
         39 |         71        0.71       98.51
         40 |         59        0.59       99.10
         41 |         38        0.38       99.48
         42 |         28        0.28       99.76
         43 |         13        0.13       99.89
         44 |          4        0.04       99.93
         45 |          3        0.03       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 , 22 Dec 2015