Frequencies for first 10,000 rows of dmage variable in natl1983 dataset :

     Age of |
     Mother |      Freq.     Percent        Cum.
------------+-----------------------------------
         13 |         11        0.11        0.11
         14 |         32        0.32        0.43
         15 |        112        1.12        1.55
         16 |        232        2.32        3.87
         17 |        402        4.02        7.89
         18 |        532        5.32       13.21
         19 |        677        6.77       19.98
         20 |        691        6.91       26.89
         21 |        679        6.79       33.68
         22 |        731        7.31       40.99
         23 |        705        7.05       48.04
         24 |        668        6.68       54.72
         25 |        713        7.13       61.85
         26 |        601        6.01       67.86
         27 |        591        5.91       73.77
         28 |        510        5.10       78.87
         29 |        469        4.69       83.56
         30 |        333        3.33       86.89
         31 |        302        3.02       89.91
         32 |        253        2.53       92.44
         33 |        175        1.75       94.19
         34 |        150        1.50       95.69
         35 |        126        1.26       96.95
         36 |         87        0.87       97.82
         37 |         69        0.69       98.51
         38 |         49        0.49       99.00
         39 |         40        0.40       99.40
         40 |         19        0.19       99.59
         41 |         18        0.18       99.77
         42 |         13        0.13       99.90
         43 |          2        0.02       99.92
         44 |          4        0.04       99.96
         45 |          2        0.02       99.98
         46 |          1        0.01       99.99
         47 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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