Frequencies for first 10,000 rows of dmage variable in natl1969 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         10 |          1        0.01        0.01
         11 |          1        0.01        0.02
         12 |          1        0.01        0.03
         13 |         10        0.10        0.13
         14 |         50        0.50        0.63
         15 |        126        1.26        1.89
         16 |        283        2.83        4.72
         17 |        444        4.44        9.16
         18 |        647        6.47       15.63
         19 |        769        7.69       23.32
         20 |        822        8.22       31.54
         21 |        839        8.39       39.93
         22 |        799        7.99       47.92
         23 |        654        6.54       54.46
         24 |        592        5.92       60.38
         25 |        552        5.52       65.90
         26 |        555        5.55       71.45
         27 |        456        4.56       76.01
         28 |        351        3.51       79.52
         29 |        300        3.00       82.52
         30 |        271        2.71       85.23
         31 |        247        2.47       87.70
         32 |        224        2.24       89.94
         33 |        171        1.71       91.65
         34 |        158        1.58       93.23
         35 |        115        1.15       94.38
         36 |        122        1.22       95.60
         37 |         87        0.87       96.47
         38 |        113        1.13       97.60
         39 |         72        0.72       98.32
         40 |         64        0.64       98.96
         41 |         43        0.43       99.39
         42 |         28        0.28       99.67
         43 |         11        0.11       99.78
         44 |          7        0.07       99.85
         45 |          7        0.07       99.92
         46 |          2        0.02       99.94
         47 |          3        0.03       99.97
         48 |          1        0.01       99.98
         49 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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