Frequencies for first 10,000 rows of dmage variable in natlterr1996 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         12 |          1        0.01        0.01
         13 |         13        0.13        0.14
         14 |         46        0.46        0.60
         15 |        145        1.45        2.05
         16 |        311        3.11        5.16
         17 |        450        4.50        9.66
         18 |        507        5.07       14.73
         19 |        620        6.20       20.93
         20 |        634        6.34       27.27
         21 |        628        6.28       33.55
         22 |        598        5.98       39.53
         23 |        633        6.33       45.86
         24 |        650        6.50       52.36
         25 |        580        5.80       58.16
         26 |        523        5.23       63.39
         27 |        499        4.99       68.38
         28 |        509        5.09       73.47
         29 |        441        4.41       77.88
         30 |        370        3.70       81.58
         31 |        383        3.83       85.41
         32 |        261        2.61       88.02
         33 |        238        2.38       90.40
         34 |        211        2.11       92.51
         35 |        173        1.73       94.24
         36 |        156        1.56       95.80
         37 |        132        1.32       97.12
         38 |        109        1.09       98.21
         39 |         67        0.67       98.88
         40 |         45        0.45       99.33
         41 |         41        0.41       99.74
         42 |          9        0.09       99.83
         43 |          8        0.08       99.91
         44 |          3        0.03       99.94
         45 |          3        0.03       99.97
         46 |          1        0.01       99.98
         47 |          1        0.01       99.99
         48 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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