Frequencies for first 10,000 rows of dmage variable in natl1997 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         12 |          1        0.01        0.01
         13 |          7        0.07        0.08
         14 |         43        0.43        0.51
         15 |        113        1.13        1.64
         16 |        226        2.26        3.90
         17 |        360        3.60        7.50
         18 |        486        4.86       12.36
         19 |        563        5.63       17.99
         20 |        598        5.98       23.97
         21 |        647        6.47       30.44
         22 |        599        5.99       36.43
         23 |        565        5.65       42.08
         24 |        556        5.56       47.64
         25 |        582        5.82       53.46
         26 |        604        6.04       59.50
         27 |        573        5.73       65.23
         28 |        516        5.16       70.39
         29 |        476        4.76       75.15
         30 |        433        4.33       79.48
         31 |        383        3.83       83.31
         32 |        353        3.53       86.84
         33 |        300        3.00       89.84
         34 |        243        2.43       92.27
         35 |        214        2.14       94.41
         36 |        171        1.71       96.12
         37 |        119        1.19       97.31
         38 |         84        0.84       98.15
         39 |         72        0.72       98.87
         40 |         47        0.47       99.34
         41 |         28        0.28       99.62
         42 |         16        0.16       99.78
         43 |          9        0.09       99.87
         44 |          9        0.09       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 , 22 Dec 2015