Frequencies for first 10,000 rows of dmage variable in natl1999 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         12 |          3        0.03        0.03
         13 |         10        0.10        0.13
         14 |         24        0.24        0.37
         15 |        104        1.04        1.41
         16 |        185        1.85        3.26
         17 |        317        3.17        6.43
         18 |        464        4.64       11.07
         19 |        588        5.88       16.95
         20 |        634        6.34       23.29
         21 |        635        6.35       29.64
         22 |        664        6.64       36.28
         23 |        554        5.54       41.82
         24 |        582        5.82       47.64
         25 |        571        5.71       53.35
         26 |        569        5.69       59.04
         27 |        553        5.53       64.57
         28 |        549        5.49       70.06
         29 |        482        4.82       74.88
         30 |        464        4.64       79.52
         31 |        369        3.69       83.21
         32 |        321        3.21       86.42
         33 |        309        3.09       89.51
         34 |        271        2.71       92.22
         35 |        198        1.98       94.20
         36 |        139        1.39       95.59
         37 |        157        1.57       97.16
         38 |         78        0.78       97.94
         39 |         87        0.87       98.81
         40 |         43        0.43       99.24
         41 |         35        0.35       99.59
         42 |         21        0.21       99.80
         43 |          8        0.08       99.88
         44 |          7        0.07       99.95
         45 |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015